With proxy problems with authentication

Hello,

We are using the Azure Application Gateway as an proxy to gsad. We are able to logon, but when the next pages wants to load we get a 401.

Logon directly without Application Gateway works fine.

gsad is running: gsad --port=9392 --http-only

Request 1
POST /gmp
200 OK
Response:

<envelope><version>21.4.4</version><vendor_version></vendor_version><token>373e892b-aeac-4313-a6f6-3aa8bcb38de1</token><time>Thu May  5 09:28:39 2022 GMT</time><timezone>UTC</timezone><login>admin</login><session>1651757319</session><role>Admin</role><i18n>Browser Language</i18n><client_address>10.60.255.38</client_address><backend_operation>1651742919.70</backend_operation>(null)</envelope>

gsad.log
gsad gmp:MESSAGE:2022-05-05 09h28.39 GMT:74091: Authentication success for 'admin' from 10.60.255.38

Request 2
GET /gmp?token=373e892b-aeac-4313-a6f6-3aa8bcb38de1&cmd=get_capabilities
Cookie: GSAD_SID=54acf966-0ce0-4047-8d76-d00814db5463
401 Unauthorized
Response:

<envelope><version>21.4.4</version><vendor_version></vendor_version><gsad_response><title>Authentication required: handler_send_reauthentication:476 (GSA 21.4.4)</title><message>Token missing or bad. Please login again.</message><token></token></gsad_response></envelope>

gsad.log
no log entries

What could be the cause of this issue?

Kind regards,
Bastiaan