Probably need to rebleed master if it rand dry, aka bench bleed.
Then the entire system should be bled this ensure no air in any line and also fresh fluid throughout system.
Start at RH Rear then LH Rear, then RH Front then LH Front.
I use a long clear tube into a clear catch can sealed tight, the tube going from bleeder into catchcan sets near the bottom.
I take some fluid and fill just over the end of tube in catch can, This allows a good one person bleed. I raise the catch can, coat hanger wire etc and suspend it higher than the wheels thus when I pump fluid through it allows air to climb UP to the catch can, this then slowly works it out of system and into can. I can see the can in my mirrors and watch for clear fluid with no bubbles then I know it's bled.
If need be i can attach a vacuum pump onto the catch can and create a vacuum to draw fluid into container.
JM2CW