can't create events or categories

trying to set up a website for the local american legion and add events to their site, installed JEM 2.2.0 and was able to create two groups, but I can't create categories or events.

Hi, can you give more informations about your system. You are in backend?

Yes, logged in as super user. Can't create categories and hence can't create events. This is a brand new site with not much on it as I'm still adding pages and menu items as I have time. I've tried uninstalling and reinstalling the jem event package and even upgraded it to the 2.2.1 today and still no dice. On event or category, I get no error messages, you can't cancel or anything, you have to hit back to get out of it.

I can't reproduce your issue:
I made a fresh and clean install of joomla 3.7.1 and JEM 2.2.1 (multilingual) on php 7.1.3. (no other plugins, modules and templates. I am using the protostar template.
I am in backend as superuser and create first a category. Then I create an event.
There are no problems!

It seems you have installed some additional things which interferes with Joomla and JEM. So I will be sure you will encounter more problems not only in JEM.
EDIT:
Perhaps it helps, if you consult the help in backend!