Microsoft Access does support multi-user but you must have the proper configuration of the Application side, i.e. Microsoft Access. Essentially you will need to properly configure your database to have both back end and front end capabilities to allow multiple users to access and modify the same database. The back end will be the tables stored on the storage device, in this case, NetApp CVO, and the front end will be a local copy on each user's local system that links back to the back end. Please reach out to Microsoft for assistance with proper configuration for multi-user accessibility.
By default, files are typically only modifiable by a single user through a file locking mechanism to avoid data being overwritten, which can corrupt a file, mainly databases. This is not unique to NetApp but an industry standard.
Can you provide more details so we can see if the issue is on our end or not?