[keycloak-user] Client authentication with signed JWT failed: Token is not active

Hello I have observed error-messages from Keycloak with this content: {"error":"unauthorized_client","error_description":"Client authentication with signed JWT failed: Token is not active"}) response: {"error":"unauthorized_client","error_description":"Client authentication with signed JWT failed: Token is not active"} Scanning for an explaination to find out how this can happen did not yield to a sufficient answer and Keycloak's code did not really clear up the problem. Perhaps the problem can be mitigated by setting the token-expiration value in keycloak.json (which unfortunately seems not be explained in Keycloak's docu), which is set to it's default here, i.e. "token-expiration": 10? If someone has any idea or experience on how this error could have come up, it would be nice to let me know? Best regards, Eduard Matuszak