2005 Volvo Xc90 temperature not working after therm and temp sendor replaced.
 

Hello everyone. I replaced the thermostat on my 2005 Volvo xc90 and the temp sensor which came with it attached. The temperature gauge was not working so I thought easy fix. Once I was done I idled the vehicle and turned on the heat. The vehicle now has nice heat but the gauge did not move. Car was idle for 15 minutes in a garage temp outside 55 degrees. Any ideas of what could be the cause of gauge not reading engine temp?
thanks

Update:
 

After driving a couple miles the temp gauge is fully functional. No issues cooling system problems so far at this time. Now to work on that darn ICM issue.