Trim gauge not working...

i have a 2005 fiesta fee that i had to put a new volvo dps-b lower unit on. I had the old dpd that fell apart inside. After the install of the lower unit my trim gauge no longer works and the shop said that they might not match together?  Ihave checked the gauge and it is fine. Any help would be appreciated!! The gauge is a 2 wire and the sending unit is 3 wire