I am getting a bit desperate now. I have been to various ubuntu sites to check on what my login details were. I found that I had a few years ago had a different auth.json ID and I deleted that from my laptop but the problem (of not being able to update snaps) persists. I can successfully login at the command line but I cannot refresh, either at the command line or in Ubuntu Software.
How can I erase all my snap history and start again, from scratch?