2001 Vauxhall Frontera no first gear

problem started when car went into limp mode, took to garage diagnostic showed fuel pump, no probs got re cond, ecu repaired and tested and immobiliser re programmed, they drove it back to me and explained no first gear, trust this garage use all the time, what happens is reverse works fine put into drive nothing, push winter mode it will pull away but this uses 3rd , leave engine running 20 mins trans light comes on but then lets you pull away manually in 2, 3 and D for fourth but never first, diagnostic now shows p0722 no output speed sensor circuit, up to now ive changed speed sensor, drained trans fluid cleaned filter etc all to no avail, also must point out speedo works perfectly,
any help or views greatly appreciated