ABS & handbrake light on still after ABS CHANGED


wonder if anyone could help. I have a 58 dci Micra k12.The ABSand handbrake light came on. Took it to my garage and an auto electrician and both said need new ABS. I had it changed but today both lights came back on.
Does anyone know what it could be?
Also, it went to an auto electrician and my mechanic before they replaced the unit and the both said the same. My mechanic has been a friend of mine for 20 years so he’s not out for profit because I got some of the money back because I have warranty