Unable to Log on to PS4

A question about : Unable to Log on to PS4

Hopefully somebody can help here. Grandson got a PS4 and has been using it to play Fifa15. He says he logged out and when trying to log back in using his Hotmail.co.uk email address it is coming up with an error message 'Cannot sign in using another players sign-in ID' He says that he is using all the correct email address and password details. I have used Google to try get round this but some of the answers say you have to create a new account but surely that will mean he will lose all the credits etc which have cost a few quid. Daughter has tried calling Sony but is stuck in a queue for ages so just hangs up. Can anyone help here, anything is appreciated, thanks.

Best answers:

• i know there have been issues with psn recently due to a cyber attack. it may be related to that. also i believe there have been online issues with this specific game. can they get online with any other games? if yes then its an issue related to the game.
• An update to the problem. Daughter managed to get through to Sony on the 31st. She says they have looked into this issue, spoke to grandson to confirm player id's etc and all they need to do now is send an email with a link to reset the PS4. Obviously over the holiday period they are shut but hopefully this problem will be resolved soon and grandson will not lose credits bought so far. Will wait and see what happens, thanks for help so far folks.