We recently moved our site to another server and migrated from moodle 3.1 to 3.6. Since then the mobile application stopped working and displays a popup error after we open the application: The web service function is not available.
We made sure to enable the web service function, checked all mobile settings, tested the REST, SOAP and XML-RPC web services and they all succeed.
There is a weird "Certificate Chain invalid" message on the mobile settings page. I checked the SSL certificate and tested it on SSL Labs and everything seems to be valid.
Please let me know what could be the issue. The site is now configured to open as http. We were facing the same issue even when the site was in https.
Thank you for your support