I'm getting a 400 error when trying to do a search both through the Graph Explorer and through my own code. Both worked a few weeks ago but have stopped working recently. Another developer has been able to replicate it in their Tenancy, but Microsoft will not provide me support as we are not a Premier Customer.
If I run this query:
https://graph.microsoft.com/v1.0/drives{drive_id}/root/
it succeeds and returns information about the drive.
Following the documentation at https://docs.microsoft.com/en-us/graph/api/driveitem-search?view=graph-rest-1.0&tabs=http a search can be used via
https://graph.microsoft.com/v1.0/drives/{drive-id}/root/search(q='foobar')
But this returns a 400 error with "One of the provided arguments is not acceptable."
However, if I search for items in our entire Tenancy via the group search it succeeds so it doesn't appear to be a permissions error, but is not a viable solution as I need to search a particular drive.