I have a 6 year old Frigidaire Gallery side by side FGHS2631PF4A. Several times over the years I have had issues with the fridge side not cooling at all and the user interface number display going out, but the freezer was always fine. To resolve the issue over the years, each time I had to replace one or all of the following:

Board Main Power AP5954594 (4 times)
Temp Sensor AP4032998 (2 times)
User Interface AP7017395 (3 times)

Yesterday I replaced all three and the fridge is still not getting cold.

I first replaced the User Interface so I could see the temp displays. Freezer was 0 and fridge side would move slowly between -32 and 0 over the course of a couple of hours, but hung around 0. The fridge was really around 55 - 60 with no sign of any air coming through.

I put in 2 different new temp sensors, but there was no change so I put in the Main Power board and now the fridge side just says OP. I have used 3 different temp sensors and all give the same results.

I also ran a diag just to make sure the OP was not due to a fridge door sensor, but the test showed the door sensor was properly detecting opening and closing.