Hi there!
Thanks for getting in touch! Yes, this would certainly be the reason for the warning message you’re receiving–you’ll need to ensure that the version numbers for both The Events Calendar and Events Calendar PRO are identical to prevent code conflicts between the two! If you’re having trouble updating Events Calendar PRO to its latest version, check to ensure that your product license is still current, as expired premium licenses won’t allow you to receive plugin updates from the server.
I hope that helps! Please note that this forum is generally reserved for pre-sales inquiries, so any further questions will be better served with a post to our Events Calendar PRO forum. You’ll need to log in using an account with a current PRO license to make a post there.
Thanks, and let us know if there’s anything else we can do to assist! 🙂