"This subscription type no longer exists: it may have been moved to the trash."

Where: student profile, Subscriptions block > Add a subscription (owner).

Why: the chosen type was moved to the trash between opening the sheet and saving, for example from another device.

What to do: close the sheet and open it again to see the current types. To use the type again, the owner can restore it for 30 days in Settings > Data > Trash.