Galaxy8 Tablet

I'm sorry no one has answered your posting and I honestly don't know how to help you but I would suggest going back to the shop you bought it from. You should also google the problem as you can't be the only person to have had this problem. My daughter says that's the answer to all IT issues.
We have a local independent phone shop and they are very knowledgeable. If you have one of those you could play the 'old lady' and beg for help even if you didn't buying there.
Alternatively, contact someone who advertises that they come to your home and repair computers. They tend to know about these things these days.
If it is any comfort, many years ago I bought a psion (the fore runner of a smart phone) and it took three of us 6 months to get it online so don't despair.

Back again - I just googled 'galaxy authentication error occurred' and there is a whole discussion forum. Good luck!

Humbertbear has just done what I was about to suggest.

Thanks Humbertbear & Nelliemoser,I really appreciate your help,I have got a connection at the moment through my neighbours Wi fi (with their permission of course) But found googling the Galaxy quite an eye opener,interesting to see how many other people have had the same problem and it's not just me getting Grannystressed. I will get some advise regarding the router and let you know how I get on.

Have you tried switching it off (power off) and then switching it on again. This usually works when my tablet says, obtaining ip address and authenticating... If this doesn't work, then I have to ask my son to fix it. My tablet is a coby. Hope this is helpful.