Sounds like too much cable tension, the actuation arm on the caliper needs to return fully to allow fluid from the reservoir through to account for pad wear. Back off the barrel adjuster so that the little lock nut thing can be screwed into the arm, if that's not enough undo the cable, then move the arm on/off a bunch of times so pistons self adjust. When hooking the cable back up or adjusting barrel adjuster you want to do it so the little locknut thing can still be engaged and you're just aiming to remove and slack from the cable, no more.
Sounds like too much cable tension, the actuation arm on the caliper needs to return fully to allow fluid from the reservoir through to account for pad wear. Back off the barrel adjuster so that the little lock nut thing can be screwed into the arm, if that's not enough undo the cable, then move the arm on/off a bunch of times so pistons self adjust. When hooking the cable back up or adjusting barrel adjuster you want to do it so the little locknut thing can still be engaged and you're just aiming to remove and slack from the cable, no more.