Same problem here, will add to the already long thread.
Happened to me (and annoyed me) several times on flights and on sea with no internet-connection. 100% no reboot or reset within 24h before it happened. License is shown as "Verified" and installed on my devices years ago.
Samsung Galaxy S4, Stock Android
OnePlus 3 OxygenOS 5.0.4, Android 8.0.0
Even though there may be workarounds of some kind, when you're offline, googling for instructions and then "download and re-install..." is not an option - if it was, license-check would not be an issue in the first place.
Please, if the checking-issue can not be resolved then make the impact less frustrating and do not just stop working at all - give me a grace-period of some days, put up a nag-screen...