Code P0776, where is the pressure control solenoid B located?

The P0776 code indicates an issue with the transmission, specifically with the Pressure Control Solenoid B. Here is the location of the solenoid so you can check the electrical connector and if okay replace the solenoid. You will need to remove the fluid pan to get to the solenoid. It will be the solenoid that has a blue or orange/blue wiring going to it. Check out the images (below). Let us know if you need anything else.

Where is the pressure control solenoid b located for 2015 Nissan Altima 2.5 S?

If you check out the wiring diagrams above, you can see the solenoid wiring which shows which one it is.