A few issues I have found-
1. version mismatch. WordPress plugin page shows most recent release, current version. Actual files are not current. Event tickets plus not actually updated in 6 months.
2. Update server to validate license key is not reachable. Might be related to #1.
3. I have completely reverted to what i had 4 months ago that was working with no issues. Your latest version is broken. Your update system is broken. I stopped keeping track of the number of people on this forum having similar issues and simply reverted to an old version.