Issue with cookies and keycloak authentication on NOMAD Oasis

I am running NOMAD Oasis with Keycloak using our Active Directory for some months without issues. Since this week, logins are no longer possible, resulting in the error message: 'We are sorry... Cookie not found. Please make sure cookies are enabled in your browser.' image I tested different browsers (Firefox, Chrome, Edge, Opera) on several PCs and also on the server which runs the oasis. Also, I restarted the oasis and even removed and newly pulled the images. The error message did not vanish.

The error log from the keycloak docker container just says: 12:00:24,756 WARN [org.keycloak.events] (default task-17) type=LOGIN_ERROR, realmId=nomad, clientId=null, userId=null, ipAddress=xxx.xxx.xxx.xxx, error=cookie_not_found