Still having this ajax error issue.
I did a test. If I update WordPress to 5.5.1 but keep you plugin at v2.11.2 then the form still works. If I update your plugin then it breaks and I get the Ajax error
My site has about 8 forms, some really simple with no customisation (like the one above which still gets the ajax error) and some are complicated with hooks into APIs etc
What do we need to look for to fix this?