Nuvi 3895 not connecting to Garmin Express

Hi
I'm a newbie and apart from my introduction post, this is my first query.
Own a Nuvi 3895 with lifetime map updates.Bought it in 2013 and have updated maps once.
Am due to travel around Europe in the next week and thought I'd update the maps. However, can't get Garmin to connect to Garmin Express.
Dowloaded the latest GE, and, after advice from the Garmin tech support, went into the diagnosis menu and set it to mass storage device. But I still can't get GE to add the device.
The device isn't seen on the computer. I'm using a Garmin data cable (not just a charging cable) and have also tried other USB data cables, all the rear and front ports of my pc, and also unsuccessfully, tried on my Mac Air with the latest GE Mac download. The Garmin isn't seen on the Mac either.
By searching here, I've seen reference to damaged USB socket/plug but if the Garmin charges from the USB cable as it does, can this be the problem?
Garmin support has offered to replace the device for over £100 but it takes over two weeks and we set off early next week. Anything I can try?
Thanks