Error while trying to access web UI (MWAA)

I configured a MWAA cluster and everything was create successfull.

The web server access is public and security group allows connection on https port for my IP. When I try to access the web UI by clicking on button Open Airflow UI, the error bellow appears.

Something bad has happened.
Please consider letting us know by creating a bug report using GitHub.

Python version: 3.7.10
Airflow version: 2.0.2
Node: redact
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Error! Please contact server admin.

I searched in this github question and I was informed that is a problem with MWAA: https://github.com/apache/airflow/issues/19133

How can I solve this or how can I debug, to find the issue?

Thanks in advance.