2007 Volkswagen Jetta - Brake issue

I installed a new set of rear brake pads and rotor on my car.
I noticed one of the caliper piston is not pushing out of the caliper after pumping the brake padel a few time and adjusting the handbrake cable, Now there’s no foot brake and handbrake on one side. It’s a
Polo 1,9tdi please advise

Have you bled that caliper?

Did you press the caliper piston back into the bore?

Or did you rotate the piston back into the bore using this tool?