domain registrar site puzzle

I was trying to help my son who lives in the UK with a
site he has registered with buydomains.com
He sent me login details along with the address
http://www.buydomainsregistrations.com/
When my browsers try to go to that address they tell me it does not
exist. Chrome suggested I try http://www.buydomainsregistration.com/
I went there and could not log in using the details he gave me.
He checked immediately and found
http://www.buydomainsregistrations.com/ ok and successfully logged in.

He immediately changed the password in case i had been caught in some
redirecting scam.

What is happening here? Can anyone explain?

TIA
Reg

 

Sorry - forget it.
He got muddled up as to which site address he was using.

 

Sorry, it did not specifically say "does not exist"
This morning, trying to find exactly what it did say,
http://www.buydomainsregistrations.com/
took me to
https://www.buydomainsregistrations.com/Systems/LogOn.aspx?ReturnUrl=/
so it looks like they might have been working on the site yesterday,
which would have been Sunday in the USA

However my son has sorted out his problem for himself so that ends the
iissue as far as I'm concerned. There is nothing more frustrating than
someone asking for help and then feeding you inaccurate information