There is an expired tag that always appears in OAuth Manager List Client Keys page at the bottom left of the screen but nothing appears to be expired. For example, when creating a new OAuth Client and it still shows the expired label. Other than the visual tag, nothing else seems to be performing inappropriately i.e. the OAuth Clients still work access APIs.
OAuth Tool Kit 4.6.X
The tag you see is a legend for an expired token. If the client is actually expired, the expiration would look like this: