Hi @Henoch Setiadi ,
Are there any changes of your Exchange Server recently?
And will the EAC be good to login?
Please check the OWA virtual directly with Get-OwaVirtualDirectory | FL or you can recreate the OWA VD with:
Remove-OwaVirtualDirectory -Identity "Servername/owa (Default Web Site)"
New-OwaVirtualDirectory -InternalURL Https://servername.domain.com/owa
Also check the Certificate Bindings of https in IIS, they should be using Microsoft Exchange(by default) or your own CA cert(if you bought one).
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