Are you moving your arm at all after you press the start button. I just have a wrist cuff, but if I move anything after I've pushed the start button I get an error code.
400ma is not a lot of juice. Does the BP monitor have a battery compartment? IF so, just add 1.5 volts for each battery, rounding up. The BPM should have a number itself, where the adapter plugs in, and a "+" with a line pointing to the middle or the outer ring indicating polarity.
In general
2 batteries= 3V-3.7V rated adapter sometimes 5V
4 = 3V, 6V,
Check that you have power and that there is a lit LED when a massage attachement is put into the top. Otherwise check this link for further instructions and power issues.
The 3 Best Handheld Percussion Back Massagers Under 50 Back Pain Relief...
http://back-pain-relief-products.net/handheld-percussion-back-massagers/
