I found out I set both a private endpoint (metered) and access via a virtual network (unmetered). Traffic apparently went via the private endpoint. I could not find a way to explicitly choose between the two connection methods. I had to delete the private endpoint, after rejection the mounting failed.
If you have the same problem, go to your storage account, networking:
- on the first tab (Firewalls and virtual networks) set to selected networks and add your virtual network, press save
- on the second tab (Private endpoint connections) delete all private endpoints
If anyone knows how to access your storage via a private endpoint from outside azure and via virtual network from inside, please let me know!