It looks like you may be using a minifier and sometimes those sort of tools can inadvertently corrupt the files they are attempting to minify. In the first instance can you try deactivating whatever is doing that and test to see if that resolves the problem?
I do note that you already tried switching to a default theme, but if the above doesn’t help by itself can you repeat that and at the same time also deactivate all other plugins except for The Events Calendar and Events Calendar PRO?
You were right on the money; we disabled the minification, and the menu was shown as expected.
While it’s not the responsibility of Modern Tribe, do you have any thoughts on how we can get W3-Total cache minification and The Events Calendar working together?
I believe W3TC can make exceptions whereby it will not minify certain scripts – so that would be one path forward here (noting also that The Events Calendar in any case ships with minified versions of its scripts which are already enqueued by default).
Really though there’s not, unfortunately, a great deal we can do where another tool further processes our own scripts.
Hope that helps – and I’ll go ahead and close this thread now 🙂