13-05-2020 19:03
Same issue here. Valid Sky Entertainment voucher purchased from Currys-PC World. Sent a complaint ticket a few days as it was looking impossible to contact them any other way. But not heard anything yet.
5 days left before it needs to be applied.
13-05-2020 19:31
OK so I fixed the issue. I don't know which step helped but here's what worked for me:
1) fix system time in Windows (my NTP server was off)
2) use Internet Explorer instead of Chrome
Then the "Hold on a sec..." message was followed by credit card charge confirmation (although the charge was in my case £0.00) and then the voucher was applied.