machine worked b4 removing 4rth axis?
machine has not worked since removing the 4rth axis?
both statements 100% true?
if so then u didnt jumper something.... bds4 has drive ready relay output that goes to a2100. not sure what ur loopback plug does so cant say whether it has jumper for this or not. u probably need to jumper these 2 wires that were in the 20pin white molex plug on front of bds4 so a2100 sees 4rth axis as "ready"