Contact form not working

I have installed Flowers template on a joomla 4 test website and keep getting an error when trying to send message -= "??Could not execute: /usr/sbin/sendmail??" - I have debug on and have tested sendmail from the global config and it works - advice?
Test site = [url] lccc.info/index.php/contact-us [/url]

Hello,

Please check if your server is capable to send emails. Check if the email is properly set in Global Configuration, according to the server's requirements. Please consult your hosting provider about the correct settings for sending emails from your site.

Also, check if your email address is correctly set (for example in the Contact component of Joomla or in the Rapid Contact module).

To confirm that email settings are correct, check if you are receiving any emails from your site. For example, check if your site is sending an email when you are using a contact form or registering a new user account.

If emails are not sent, please consult your web hosting support for help.

Regards,
Milos

Hello - I am still having a problem with the contact form not working - now on a different joomla 4 site - www.sunflowergirlfarm.com/index.php/contact-us ,

I can go to the site and send an email to me using send mail or php mail - and also I get mail when someone registers and send in an order - but the form, will not work.

I get this error with debug on:
+++++++++++++++++++in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/WebAsset/WebAssetRegistry.php (line 134)

1. Code:

   [color=var(--highlight-default)]    [/color][color=var(--highlight-keyword)]{[/color]
2. Code:

   [color=var(--highlight-keyword)]        [/color][color=var(--highlight-comment)]// Check if any new file was added[/color]
3. Code:

   [color=var(--highlight-comment)]        [/color][color=var(--highlight-default)]$this[/color][color=var(--highlight-keyword)]->[/color][color=var(--highlight-default)]parseRegistryFiles[/color][color=var(--highlight-keyword)]();[/color]
4.  
5. Code:

   [color=var(--highlight-keyword)]        if (empty([/color][color=var(--highlight-default)]$this[/color][color=var(--highlight-keyword)]->[/color][color=var(--highlight-default)]assets[/color][color=var(--highlight-keyword)][[/color][color=var(--highlight-default)]$type[/color][color=var(--highlight-keyword)]][[/color][color=var(--highlight-default)]$name[/color][color=var(--highlight-keyword)]])) {[/color]
6. Code:

   [color=var(--highlight-keyword)]            throw new [/color][color=var(--highlight-default)]UnknownAssetException[/color][color=var(--highlight-keyword)]([/color][color=var(--highlight-default)]sprintf[/color][color=var(--highlight-keyword)]([/color][color=var(--highlight-string)]'There is no "%s" asset of a "%s" type in the registry.'[/color][color=var(--highlight-keyword)], [/color][color=var(--highlight-default)]$name[/color][color=var(--highlight-keyword)], [/color][color=var(--highlight-default)]$type[/color][color=var(--highlight-keyword)]));[/color]
7. Code:

   [color=var(--highlight-keyword)]        }[/color]
8.  
9. Code:

   [color=var(--highlight-keyword)]        return [/color][color=var(--highlight-default)]$this[/color][color=var(--highlight-keyword)]->[/color][color=var(--highlight-default)]assets[/color][color=var(--highlight-keyword)][[/color][color=var(--highlight-default)]$type[/color][color=var(--highlight-keyword)]][[/color][color=var(--highlight-default)]$name[/color][color=var(--highlight-keyword)]];[/color]
10. Code:

    [color=var(--highlight-keyword)]    }[/color]
11.  

WebAssetRegistry->get('preset', 'template.cassiopeia.ltr') in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/WebAsset/WebAssetManager.php (line 263) WebAssetManager->useAsset('preset', 'template.cassiopeia.ltr') in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/WebAsset/WebAssetManager.php (line 197) WebAssetManager->__call('usepreset', array('template.cassiopeia.ltr')) in /home/customer/www/sunflowergirlfarm.com/public_html/templates/sparky_framework/error.php (line 58) require('/home/customer/www/sunflowergirlfarm.com/public_html/templates/sparky_framework/error.php') in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Document/HtmlDocument.php (line 721) HtmlDocument->_loadTemplate('/home/customer/www/sunflowergirlfarm.com/public_html/templates/sparky_framework', 'error.php') in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Document/HtmlDocument.php (line 776) HtmlDocument->_fetchTemplate(array('template' => 'flowers', 'directory' => '/home/customer/www/sunflowergirlfarm.com/public_html/templates', 'debug' => true, 'csp_nonce' => null, 'templateInherits' => 'sparky_framework', 'params' => object(Registry), 'file' => 'error.php')) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Document/HtmlDocument.php (line 612) HtmlDocument->parse(array('template' => 'flowers', 'directory' => '/home/customer/www/sunflowergirlfarm.com/public_html/templates', 'debug' => true, 'csp_nonce' => null, 'templateInherits' => 'sparky_framework', 'params' => object(Registry), 'file' => 'error.php')) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Document/HtmlDocument.php (line 630) HtmlDocument->render(false, array('template' => 'flowers', 'directory' => '/home/customer/www/sunflowergirlfarm.com/public_html/templates', 'debug' => true, 'csp_nonce' => null, 'templateInherits' => 'sparky_framework', 'params' => object(Registry), 'file' => 'error.php')) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Document/ErrorDocument.php (line 139) ErrorDocument->render(false, array('template' => 'flowers', 'directory' => '/home/customer/www/sunflowergirlfarm.com/public_html/templates', 'debug' => true, 'csp_nonce' => null, 'templateInherits' => 'sparky_framework', 'params' => object(Registry), 'file' => 'error.php')) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Error/Renderer/HtmlRenderer.php (line 78) HtmlRenderer->render(object(Exception)) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Exception/ExceptionHandler.php (line 126) ExceptionHandler::render(object(Exception)) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Exception/ExceptionHandler.php (line 72) ExceptionHandler::handleException(object(Exception)) in /home/customer/www/sunflowergirlfarm.com/public_html/libraries/src/Application/CMSApplication.php (line 322) CMSApplication->execute() in /home/customer/www/sunflowergirlfarm.com/public_html/includes/app.php (line 61) require_once('/home/customer/www/sunflowergirlfarm.com/public_html/includes/app.php') in /home/customer/www/sunflowergirlfarm.com/public_html/index.php (line 32) PHPMailer\PHPMailer\ ExceptionCould not instantiate mail function.
+++++++++++++++++++

Advice?

Hello,

The last line of the error log says that the PHPMail function is not available on the server. Please consult the hosting support.

Regards,
Milos