I installed version 6.1 Build 6123 on Exchange 2019 CU12 on Server 2019

I manually added the inbound firewall rule for the admin portal (as it could not work without this)

I was blocked initially by Configuration:MFA:MFA for endpoints requiring HTTPS  - even though this was enabled, and I was logged into the admin console over SSL/HTTPS with a valid certificate.

I found I had to set BOTH Admin:ConnectionSettings:https AND Admin:ConnectionSettings:Configure Access URL

The second was not obvious

Is it worth making this easier to spot?

Thanks