Drivers side rear indicator not working

[AlexP]

Hi, I’m at a lose here, my drivers side rear indicator isn’t working. It hasn’t brought up a bulb warning, if I swap rear light units it works on the passenger side and the passenger side that does work doesn’t when plugged into drivers. So nothing to do with the unit itself. It’s a 2005 seat altea
If anyone can help I’d appreciate it
Thanks