It seems like your tag is either overwritten or some application is stopping the unlock app from registering the ring.
please try to remove the tag in the unlock app an then add it again. Please note that the tag which is used for unlocking (with the NFC ring unlock app) can not be used for something different than unlocking.
hope this helps.
@JimmyDingDongs did you try this? Try registering both sides as keys, and then test.
If you can still access the app using the ring then the ring still works, it's just not launching the unlock properly when the phone is locked.
Unlock App writes data to the inlay which must be retained unaltered in order for it to work.
Alternatively, if you're rooted then why not try something else that will allow you to bypass the standard lock screen using a ring?