Has Forti SRA different GUIs?

Hi together,

we are actually implementing Forti SRA for remote access for our admins. We installed the SRA VM in our DMZ, only one interface with a RFC1918 IP address. On the Fortigate in the datacenter we have a VIP forwarding an external IP to the SRA.

Connecting to the SRA is possible but it seems that there are two different GUIs in the SRA (look at the screenshots attached). Sometimes one appears, sometimes the other. We didn't find out yet on what it depends. If the "well-known" Fortinet GUI appears, there is a message

Connection to the interface IP address via the GUI is only used for uploading the license. All FortiSRA configuration should be performed by connecting to the proxy address

Also after logging in via this way if one accesses the secrets there is a message

The feature is not available on interface IP.

It does not depend on the browser used (Chrome, Edge, Firefox), the browser plugin is installed in every browser.

When the Forti SRA Login page appears everything is fine.

When connecting to the Proxy address as requested by on of the messages (https://FQDN:8080) there is a "PR_END_OF_FILE_ERROR".

Can anyone help with that? If there is more information needed, please advise which config options we should share.