How do I check if Ajax is working on my site?

Hi

I tried using BuddyPress a while ago but was unable to make replies because the button needed to submit replies was not appearing - I think it was possibly because Ajax was not working on my site. I'm not going with buddypress now (for a different reason) but I'd still like to know if Ajax was the source of the problem.

How do I check if Ajax is working on my site?

The URL is https://conflictcomms.org but the site is private and needs a login to access it.