Exchange ECP not working on new installation

Question

Hello,

I've been looking for a few days now and tried a few suggestions but none of them helped so far.
I have installed a new Server 2016 with Exchange 2016 CU20 because our old Exchange server failed.
Everything seems to be fine except for the ECP page, it just won't load.

After logging in ECP I get the following page (this also happens on the local server and when a normal users logs in to ECP):

I've set all the paths for ECP, OWA, PowerShell, etc.... to the correct URL.
I also tried to rebuild the pages using UpdateCas.ps1 but this also doesn't help (OWA seems to be working fine, not tested 100% though).

In Chrome Developer Tools (F12) I see below errors:

And in Internet Explorer Developer Tools (F12) I see below:

What am I doing wrong here?

Answer 1

Hi @Cris Kolkman ，

From the first screenshot you shared above, it seems the issue is similar to what is described in the official document below:
Missing images in ECP

Please go to Control Panel > Programs > View installed updates, check if the April 2021 Security Updates(KB5001779) for Exchange 2016 CU20 has been installed. If this is the case, as suggested in the link above, please uninstall the update(KB5001779), download the .msp file from this link, run command prompt as administrator and run MSP from there, then reboot the server and check if the issue persists.

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