Rang Samsung help desk and a nice lady re set my TV. It worked....for a while. It stopped working after a couple of hours. I think it's a bbc issue as the previous week I player was perfect. A bodged update I think. As a licence player I think it should be free to all, not logging in for any reason.
I think it was update-related when I had the issue too - I had been updating Plex and putting some other stuff on I think. My iplayer is still working fine since the reset though.
I do login with mine ... but didnt realise that was mandatory now. Seems a bit of a surprise because I doubt that everyone has a BBC account.
There are a few threads on this.
Best thing to do is to phone Samsung support.
One other possible solution that was recently posted was to go to the BBC News app on your Smart Hub and update that ... it appeared to fix someone's iplayer issues.