Already tried all these things. I learned the window sync is for vehicles made after Jan 94. Mine is a 94 model 600SL, made in late 93.

Tried window sync anyway - no change

Here are the trouble codes I can read (for the soft top controller, read from pin 21 in the 38-pin datalink connector): 7, 8, 17, 18, 20, 21, 22, 29
I cannot clear them (tried reading them and then shorting to gnd pin 21 for 8-10 seconds after each code)

hydraulic oil (pump and tank located in trunk) is full, no leaks

I'm running out of things to try... I'll buy the darned scanner before I take it back to the dealer and get plundered and pillaged once again for something that should be a simple reset.