No power to radio but fuses seem ok?

[points]

I have a 2012 Vito 113 CDI and am trying to install a cheap head unit. I was having no luck and decided to test the main loom to see if there was power. Initially the test lamp lit, but then there was a click from the passenger footwell area and no power. I have checked the fuses in the engine bay and they all seem ok? Also the fuses below the passenger seat. I wish I'd not started on this project. Does anyone have any ideas?
Thanks