Replacement Shay power truck not picking up power

[Waikiki968]

Recently replaced (3/2020) rear power truck on 2-truck g-scale Shay no longer picks up power from the wheels.  I have removed the axles and cleaned the pickups and back of the wheels.  When power is applied to the bare pickups nothing happens, as is the case when power is applied to the re-installed wheels. 

When the truck is fitted to the locomotive and power is applied to the front truck wheels, the rear truck operates normally. 

Any ideas? 

Thx. 

[Homo Habilis]

Have you reviewed George Schreyer's page for the Shay?

http://www.girr.org/girr/tips/tips1/shay_tips.html#contacts

Perhaps there is something that will be of use to you.