Alertmanager is not ready yet

Hello everyone and happy new year,
for several weeks I’ve had a problem with alerts in grafana.
Here is the message:
level=error msg=“Failed to apply Alertmanager config for org” org=1 id=23 error="unable to apply configuration: failed to validate integration "Test03" (UID LC36VPx4z) of type "slack": invalid URL
When I want to reset my configuration I get the following message : Failed to reset Alertmanager configuration: Alertmanager is not ready yet
The same applies if I want to delete the rest of the configuration.
There doesn’t seem to be a problem with the rest of my grafana configuration.
Are you aware of this problem? I’d like to force the deletion of the alert configuration.