SGC MAC-200 won't go into AUTO mode

[bbo14]

I have looked on this forum for any related info. Finding nothing, I would like to ask if anyone here has, or has used, an SGC MAC-200 autotuner? Mine will NOT change from MANUAL to AUTO tuning mode. The user manual tells how to put it into the MANUAL mode, but says nothing about changing back to AUTO. I have tried RESET and removing all DC power from the tuner, but it seems to want to stay in MANUAL. Does anyone have any experience with this tuner? Thanks in advance.