car sags in the front
 

hi, i have SL 1995 with ADS. 2 weeks ago, tie rods and lower control arm bushing were replaced. Hydraulic suspension fluid was bled in the front and back. a few days after, i noticed that the car lost its height in the front but still maintain height in the back to the point that tires hit fenders and was not drivable. it was towed to independent shop. i was told that linkage was ok. they try to bleed hydraulic fluid but can not get the front to move up. what should we be looking for? or car need to be towed to dealer this time.
regards,
mike