Office Web Apps Server Issue: Something went wrong, an error has occurred

Some days ago, I had to rebuild our Office Web Apps Server (aka Office Online) connection to the SharePoint Farm. An easy task I thought. But suddenly I got following error while opening a document in the browser:

Sorry, something went wrong
An error has occured.

After digging in the ULS Logs (loglevel has to be set to default) I came across those errors:

Exiting GetWOPITargetInternal Early - GenerateWacUrl failed to produce a URL/actionEntry for file

and also

SPShareByLinkHandler.Initialize : Not a ShareByLink request - missing access token

The issue was that the SPWOPIZone was not the same as the SPWOPIBinding Setting. I used "internal-https" in SPWOPIBinding and "external-https" as SPWOPIZone. Setting both to the same value resolved this issue:

set-spwopizone "internal-https"
set-spwopibinding "internal-https"