Hi Jason!
Thank you for reaching out!
It sounds like you may have a conflict going on somewhere. Possibly a JS conflict with either your theme or another plugin.
For that particular tooltip hover view on the main calendar, you do not need Events Calendar PRO. PRO does add in special (and awesome) recurring events that also carry it’s own set of tooltips elsewhere in event lists.
You’re welcome to snag a license of Events Calendar PRO, to which we’d be able to help you out here in our Premium Forums, or if you’re cool with the free version, you’re welcome to post on our dot org forum.
Have an excellent day!