@sneakypete What are you trying to log in with? Use the same browser and device that you paid the subscription with/ changed the passwords with... Any joy?
As an aside ALL my online subscriptions are made inside my Firefox browser, and since I log into the browser, any user names or passwords are automatically saved by the browser and distributed across all my devices that carry Firefox - Which is all if them. So no matter what I log into a channel with, the user and pwd are always there, and it does not get lost.
Secondly, if your browser has recorded the password it may have recorded more than one. Be sure you are only being offered one choice, or it may be another.
And lastly, most sites require a registered device, and may have more than one instance of that device logged at the site. You should be able to get to your account on the site with about any device (even if it won't let you play) and go look at registered devices in your account settings, and clear out all instances except the current one, or current ones, if you use more than one device to access the site. If any question, just get rid of them all and re-register devices as you access again each time.
Hope that helps.