Could it be your defines for your ADC being in mixed case? I was reschooled in that recently.

On your OSCCON statement, are the last 4 bits what you want? Assuming you're using an internal oscillator, Bit 3 should be 1 for internal clock, Bit 2 should be 1 for stable clock, Bits 0-1 as 00 uses Fosc to set oscillator.

ADCON1 bits 0-3 are undefined. I'm assuming you want your Vref to be right justified with Vref and AVss so the ADCON1 should look like this 10110000. It says in the data sheet you need to set ANSEL AN2 and AN3 to inputs to use Vref. So make sure to change your ANSEL settings to 00001111 for AN0 to AN3 as inputs.

I'm also wondering if your ADCON0 bit 2 should be a 1 to start the conversion process. If it's a 0 I wonder if the conversion process will even begin.

I'm also assuming TRISB is for a part of the program not shown.

All that said I'm not a true "programmer" and I must just be creating more fodder. Best wishes.