MicrosoftPaul_Huijbregts Thank you for your response. I've double checked all 3 points mentioned and all are fine.
Running the analyzer Tool, I stumbled across something. The log is showing the following errors:
Connectivity output, using psexec -s:
Proxy config: Method=TelemetryProxyServer, address=xxxxxxx.ads:3128
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Testing URL : https://winatp-gw-weu.microsoft.com/commands/test
1 - Default proxy: Failed (12002: WinHttpSendRequest: 12002: The operation timed out)
2 - Proxy auto discovery (WPAD): Failed (12002: WinHttpSendRequest: 12002: The operation timed out)
3 - Proxy disabled: Failed (12002: WinHttpSendRequest: 12002: The operation timed out)
4.1 - Named proxy ( xxxxxxx:3128): Failed (0: SSL error: WINHTTP_CALLBACK_STATUS_FLAG_CERT_REV_FAILED failed to check revocation status. )
5 - Command line proxy: Doesn't exist
I've already followed: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn265983(v=ws.11) since our servers are disconnected from the internet. Unfortunately, this did not improve the situation. Weird thing, when opening https://winatp-gw-weu.microsoft.com/commands/test in the browser. The certificate is indeed invalid but maybe that's expected. I'll keep investigating further as this can't be unsolvable. Something seems to be weird here.
I'm happy about any tips where to look, all keep you posted about the progress.