hudojnyk

@bertpc Is it possible you might be looking in the wrong spot for theme options? Despite the name they are not part of your theme they are part of the calendar plugin and found under the Events submenu.

@gizant I’m on a built-from-scratch custom theme that is several years old. Sorry it didn’t work for you; I did figure out a very hacky work-around, before I found this thread.

I went to the Wayback machine and typed in my own site url, loaded a snapshot from a few weeks ago when the styles worked. Then using dev tools I found the url to the archived version of the cached CSS for Ai1ec that the archived page loads up. I saved that file, then uploaded it into my cache folder under /wp-content/plugins/all-in-one-event-calendar/cache/ and that fixed the issue, at least temporarily — some cache rebuild might have deleted that file in future.

The above is not ideal but may work for some people.

I was having the same problem and was about to contact the developer or post here, but the tip from @lilyhoop worked great for me. It appears to be an issue with cached CSS. The devs should be aware and fix the bug.