how can i fix my EP2001 programmer?

drained central heating to add new rad, didn't turn off electric to programmer and now it doesn't work. Had air in system but have bled all radiators produce water at bleed point but heating will not kick in. No lights on programmer and not allowing you to select programme. Is it the battery, it hasn't been changed in 6 years or is there a reset button somewhere or some other problem.
Its a potterton EP2001 programmer.