USB ports not working on my iMac G4. Have tested keyboard , USB ports not working on my iMac G4. Have tested keyboard

Just purchased a iMac G4 and none of the USB ports work. Imhave tested the keyboard and mouse on another computer and the work fine. I have also done a PRAM reset on the machine but this has not made any difference. It seems like the other connections are working (I.e external speakers) but not the USB ports.

The iMac boots up fine but I can not interact with it without the USB ports working:-( I would really like to get this working because I think it's a perfect first computer for my 8 yr old daughter.

Thanks for any help offered:-)