Hi,
Since there is no accounting information / its a non valuated material in the plant, system will ask the account assignment category in the PO. However, if you do GR for the item, system will ask you the storage location also for a non-valuated material. This is the standard behavior.
If you are getting a different behavior, check the OMS2 settings for the material type and plant combination, as already explained by experts. It should be with a quantity update indicator ans without value update indicator for the plant as shown below:
Cross check the settings and test the scenario again.
Regards,
AKPT