Authentication through web console issue

I installed Couchbase Server 6.0.0 Community (for Windows) in Windows Server 2016. After that I opened web browser and created a new cluster.
When i re-enter web console and try to authenticate with credentials I used it fails with message “Login failed. Please try again”.

Actually, it goes the same way with Couchbase Server 6.0.0 Enterprise.

I did many installs and I’m sure that is not an issue with incorrect credentials.

Please, give me some hint on what could be wrong with my install?