Most of the (self) adjustment is in the caliper, it maybe worth removing the calipers (I would do both sides) push the pistons back to make sure that they are still free and then put the calipers back on but leave the handbrake disconnected then take the car for a drive using a lot of braking.
Now unscrew the adjuster nut under the cubby and reconnect the handbrake to the calipers now adjust the nut until there is a 1to2 mm between cam and the caliper body (see the line in red) with the handbrake on.
Of course it could be that the new caliper has packed up.