The good news is that there was nothing wrong with the GPS but my battery charger was faulty. Is was recharging batteries and the red light did turn to green, however it was not fully charging the batteries.

New charger and the GPS worked straight away. I think the problem was that there was not enough charge available to get a signal but enough to power on and perform other functions.

What alerted me to the problem was that my daughter wanted a new camera as her was running out of charge constantly despite using (apparently) fully charged batteries

Why don't you contact Product.Support@garmin.com? They are very helpful and efficient.

The first time a GPS is used it can take a long while to, er, get its bearings. Just leave it on outdoors one afternoon.
Does the screen say "Acquiring" and show a bar chart of signal strengths, or perhaps a series of circles with satellite numbers?
It is also possible with Garmin devices to put the device into NON-GPS mode (ie for when you're indoors) - so check the manual and see how to change this.
I have the Foretrex, which is essentially the same software at the eTrex, and it works flawlessly every time and in all conditions. (Garfield)

Not used it for at least a year but the same problem still occurs. It just cannot pick up a satellite signal. It used to but no longer. It is an Garmin Etrex Venture, about 7/8 years old.

Everything else seems to be in full working order and the batteries were freshly recharged but after an hour on open moorland I decided it was just not going to work. I had turned it on and off a couple of times, to no avail.

Any thoughts or suggestions please.