This is only affecting Windows servers running Gurobi Remote Services 9.1.
Helmet is a security feature that may cause an issue with the Cluster Manager's Web UI. You may only see this loading screen when trying to access the Cluster Manager with your browser:
Then, you should deactivate the helmet feature by adding this line to the Cluster Manager configuration file
If you have experience with the developer console in your browser, have a look there when you experience this issue: On the console you may see an error like "Refused to execute script from '...js' because its MIME type ('text/plain') is not executable, and strict MIME type checking is enabled."