This topic seems closest to the issue I'm experiencing. I followed the instructions to start NextCloud on a clean ubuntu VM, and ran the build script linked here in this thread. Everything appears to work perfectly, including Let's Encrypt and SSL. However, whenever I try to view an office document via Collabora online, I get the "Access Forbidden" error. I can create a new document, but I can't view it. I checked that my /etc/apache2/sites-available/office.mydomain.com.conf had the patch mentioned above (it did). What else can I check?