These steps helped when Cab Sports changed gaming providers.
Try to login to V2U with the guest member id it will bypass the cache.
Look at the V2U logs if the member returned has an Id of 0 and all the other fields are null or default then look at the netpos logs
Look at the netpos logs- particularly around errors
This line Interface Type with Id does not exist means the Web App location in BackOffice is configured incorrectly.
Got to back office and change the web app member lookup settings:
Restart NetPos and WebApi:
Also check the member type standard/alternate in both the Web App Location and V2U Config For Cab Sports using Max Gaming it needed Alternate Id as the lookup field and Alternate as the Lookup Type.
This needed to be for all V2U Locations or they would get a "Cart not found". The netpos message displayed it trying to process a sale with the alternate id.