I really appreciate the quick response.
I previously tried all those things without avail.
However; today I scanned a number of times for the mooshimeter app and managed to find it on one occasion, so was connected. It said I have to update, but no amount of scanning finds the bootloader. Currently I can’t seem to find it again.
A little bit more information which might help. I can see it in my list of available devices quite frequently when I scan (not all the time). I down loaded an app called nRF Master Control Panel, which seems to find it and I think also the bootloader.