Radius Permissions Issue - HPE 1920-24G-PoE Switch (JG926A)

I've set up an HPE 1920-24G-PoE switch (JG926A) to authenticate against a Windows NPS server.  Authentication is working fine, but authenticated users do not have manager permissions.  I've set up a vendor-specific attribute as follows:

Vendor Code: 25506
Vedendor-assigned attribute number: 29
Attribute format: Decimal
Attribute value: 3

Essentially the same NPS policy (aside from this vendor-specific attribute) works perfectly on my Procurve 26XX switches with aaa authentication login privilege-mode set.

Any ideas what's going on?