lights and ecu

I have a 2008 Octavia ambiente 1.9tdi est I have just had my ecu repaired due to being fried have been advised by my mechanic that it could have happened when I was sorting out a problem with the rear lights a bulb had gone out so I changed it for anew one but that didn't work either after changing the bulb 3 times with not effect I put it all back together and it suddenly lit up but the engine would not fire up now the bulb out warning light on the dash is on all the time and all bulbs are working and no errors show up on diagnostics. if anyone has had a similar experience or can tell me why dash warning is always lit I like to hear from you.