404 when saving changes in settings

Have you tried re-saving your permalinks under Settings > Permalink? What version of Events Manager and WordPress are you using? Are you testing with the default WordPress theme?

I’ve saved my permalinks (about a few dozen times). I’m using WordPress 4.1 and Events Manager 5.5.5. This is on a newly created test system so naturally I’m using the default theme. I can send you test account credentials to assist in debugging if you would like.

That’s not an option on these forums.

Can you link to a screenshot that shows what you see when you try to save the settings (we can’t see the links you posted without being logged in)?

I didn’t post any links. I was going to send a user registration email if I could find your email (you can still provide me with one). I have some screenshots here. Main Settings.png is the settings page that I can see (this is on the test site with no plugins, themes, or WP settings changed. Its not a multisite installation, my main site is and it has the same problem.) Main Settings 2.png is the same thing but collapsed. When I click the save settings (all) then it takes me to a 404 (404.png) These are the urls:
https://dcchelp.elementfx.com/testing/wp-admin/edit.php?post_type=event&page=events-manager-options#general
Saving goes to the same url

I have seen this on my main site which has many plugins and themes but also on a completely new installation

is this using multisite or subsite installation?

The screenshots are from a testing installation which is not multisite. My actual website (not the testing website but the one in production) has this same issue and is a multisite. Essentially what I’m saying is that the issue is on multisite and non-multisite.

Have you tried using a different browser? It could be there’s an incomplete Javascript file cached in your browser that’s causing the problem.

No. It seems to happen on Firefox and Chrome, on Windows and Linux.