I have a site where I am entering my license key, clicking Save Changes and the key is recognized as valid, however it does not appear to be saving the key. After going to Dashboard->Updates, I see the following message:
“There is an update available for The Events Calendar PRO but your license key has not been entered. Please go to the Events Calendar Options page to enter your license key.”
If I go back to the Settings->Licenses tab, the key field is blank.
I have tried deactivating all other plugins and activating the default Twenty Fifteen theme, but the behaviour persists.