Hi guys,
I have a problem with a Nextcloud Instance which already exists since several years (basically since installing this instance).
Some files like .mid files won’t get synced, and I’m not sure where to start. Does Nextcloud hate music? 
The client has a setting for ignored files. *.mid files don’t make part of the default list in my client. Can be on the server side. The fileaccess-control app can block extensions, the webserver itself probably as well.
The logfiles of the client and the server can be starting points. Checkout the troubleshooting guide:
https://docs.nextcloud.com/desktop/3.4/troubleshooting.html