After changing the certificate on Exchange 2013+2016 (AND you have rebooted it – or it will happen eventually if you forget!), you may experience this when logging into ECP, you get the username and password prompt, you press login and – BAM:
You look in the event logs, and you see this:
EventID: 15021
An error occurred while using SSL configuration for endpoint 0.0.0.0:444. The error status code is contained within the returned data.
No need to be scared, this is not difficult to use, what happens is that the IIS websites are not having the new certificate set, and the certificate window under the binding in IIS is just empty:
Just click the dropdown menu, and select the correct certificate you have imported and run a IISRESET on the command prompt afterwards or even better reboot the server if possible.
This issue occurs if the SSL binding on 0.0.0.0:444 has one of more of the following issues:
- The binding is installed incorrectly
- The binding doesn’t have a certificate assigned.
- The binding contains incorrect information.
For example, this issue occurs if the certificate hash of the binding is different from that of other bindings for application ID 4dc3e181-e14b-4a21-b022-59fc669b0914.
You can also fix via command prompt:
Type “netsh http show sslcert”:
Remove and replace the wrong certificate hash for 0.0.0.0:444 by running this:
“netsh http delete sslcert ipport=0.0.0.0:444”
“netsh http add sslcert ipport=0.0.0.0:444 certhash=a1d2a8d3275634xxxxxxxxxxxxxxxxx appid=”{4dc3e181-e14b-4a21-b022-59fc669b0914}”
Note: replace certhash with the full hash of your cert!
Reboot the server or do IISRESET command 
Source:
You get a blank page after logging in EAC or OWA in Exchange 2013 or Exchange 2016 (microsoft.com)
Microsoft Exchange 2013 shows blank ECP & OWA after changes to SSL certificates | vcloudnine.de