Save, add and close buttons no longer working

I recently had to upgrade to PHP 7.4 and now the save, Save & Close, Save & New and Cancel buttons at the top of the pages do not function.  So I'm unable to add an event, Category or even modify existing events or categories.  
I'm on Joomla version 3.10.4, PHP version 7.4 and JEM version 2.3.3

which is your site. On my site I can't reproduce your issue

My site is   I have tried using Chrome, FireFox and Edge.  Should I try IE?

sorry forgot to include the  

americanlegionpost276 dot org

have you tried with the joomla official protostar template.  There are some templates and plugins which create interferences.