Magento 2.3.5-p2 Emails not sending

Question

When i submit Contact Us form on frontend i get: Unable to send mail: Unknown error and error in exception and debug logs:

main.ERROR: DOMXPath::query(): Invalid expression in selector >> .homeadv .ah-block:nth-child(3n+1) << in /var/www/html/vendor/pelago/emogrifier/src/Emogrifier.php on line 530 {"exception":"[object] (InvalidArgumentException(code: 1509279985): DOMXPath::query(): Invalid expression in selector >> .homeadv .ah-block:nth-child(3n+1) << in /var/www/html/vendor/pelago/emogrifier/src/Emogrifier.php on line 530 at /var/www/html/vendor/pelago/emogrifier/src/Emogrifier.php:2022)"} []

When i send email from orders page i get: You sent the order email. but not receiving any email

I am not sure when it stopped working, but it did worked before. All latest updates, Ubuntu 18.4, PHP 7.2.33, Magento 2.3.5-p2, hosted on DigitalOcean.

Answer 1

Solved! Followed this solution

Just had to download magento zip installer and extract required files as my

/vendor/magento/theme-frontend-blank/web/css/ was empty.