ecu swap vag.com only works for a day

hi there, i need help. ive installed a second hand ecu in my golf gti 2.0 8v 1998. my friend has vag.com 409 with lead registered etc. he done the adaptation etc and the car worked. unfortunately the next day i got in the car to start it but no fuel pump? he came round again and done the adaptation and it worked again, i stopped and started the engine a number of times and it seemed fine, but yet again the next day no fuel pump. does anyone know whats happening and how to fix it.

many thanks