This site has always used a php script for its contact forms. I purchased a very cheap script years ago that has quit working time after time. The developer always fixes for no cost but in the meantime, I’m not aware the form isn’t working.
I switched to JotForms – easy set up and works fine except SPAM. No real messages at all – just folks trying to sell me something.
I have used WPForms in WordPress so I finally gave in and installed it on this site. Most of my pages are html/php with only one “page” of blog posts which is actually a modified WordPress page.
WPForms Lite is free and enables the use of any of the google recaptchas – I now use the invisible one but still fighting spam.
The good news is that ZenCart plus the google recaptcha does seem to do the trick if you start having spam issues after upgrading. The newest version of that zen cart mod is definitely better than the old one. I never install it until a client complains ’cause this is not an issue on all sites.