BL2600 SBC Not reading volts on analog input 4

Using the anaInVolts function, I can read volts on analog input channels 0-3. When I try to read volts on channel 4 it always returns 0.003 volts. I can read raw counts on channel 4, but not volts. I tried another spare board and it did the same thing.

Any ideas why? Something to do with the BL26XX library? Thanks in advance.

It must be something in my program. I can read all inputs with the sample program. I will check my initialization code.