Error 777 indicates that applying the update code would result in an invalid setting for the simultaneous network user limit. There are two reasons this might happen:

If you are changing the dongle from a per-licence user limit to per-product, you must also set the per-product network user limit.

If the dongle has a per-licence user limit and you are adding a new licence, you must set the limit for the new licence.

Note - you would not normally change the net user limit from per-licence to per-product (or vice versa) unless you had a specific reason for doing this.