Why don't Device Attribute values show in the Device Grid unless the device does a Check-in?
Custom attributes are configured from web console and values pushed from server to devices. If you have problem in your web-console display, it's probably related to update issues in the new search module and UI in early v14.x MobiControl server. In any case, it should just been a display issue, and any new value should be pushed to the device after the next manual /automatic server-device data sync ( and manual check-in initiated from the web-console is one of such sync mechanism).
It's likely that your problem can be resolved if you upgrade your v14.x server to more recent v14.3.x. I suggest you to open an official support ticket with Soti Support team to consult about the risk and procedure for such server upgrade.