A search on this issue reveals that you might find a lot of suggestions on how to solve the problem. Here's a quite sensible link which might guide you further, written by Prashant, a Microsoft MVP for Office Servers and Service.
He shows how to go about to debug and finds the error of Trust relationship…. Saying ‘Could not establish trust relationship for the SSL/TLS Secure Channel.’ And he shows how to solve it. By no means sure, bur perhaps that could be the solution.
[Solved]Error: Sorry, there was a problem and we can’t open this document with Office Online on Exchange Outlook Web Apps
https://pdhewaju.com.np/2017/02/11/solvederror-sorry-there-was-a-problem-and-we-cant-open-this-document-with-office-online-on-exchange-outlook-web-apps/