Payment Failure

[#1]

I have just been trying to pay my yearly line rental, due on 10 February, by American Express CC  via the Plusnet website. On the two times I tried, when I pressed the 'Pay' button I simply got:
"Connection closed by remote server"
Any suggestions?

[#2]

OK. Payment now gone through on third attempt.
This was made on laptop not desktop, but this is likely not the explanation. This time I was logged in before I attempted payment. If this was necessary why did webpage linked to in email not ask for login before payment?
Also, the PN Line Rental Saver information page says to pay via link on Account Page. Nowhere can I see such a Line Rental Saver link in my PN account pages. 

[#3]

It should have done as already being logged in or via auto login shouldn't work when you are doing something which costs money
Re Line Rental Saver on the Account Page - it should be BUT it isn't despite numerous gripes