I purchased members for all my botting newbs (4 at the time) and I tried to buy a fifth but it has been declined. I tried paypal, CC, three different IPS but the same problem happens.
How many times have you purchased members on that same day with PayPal and then how many with the CC? Sometimes, JaGeX limits the number of memberships that can be bought with PayPal or CC within a time period. Happened to me before when I tried members on my accounts.
You can only buy 2 Members a month with credit card and only once with Paypal as far as Im aware. Not sure how you got the 4th but I have tried adding my paypal to a 2nd account and it won't let me.
They limit/block how many subscriptions you can buy with same PP:CC invade of hacked PP or stolen CC.
You could contact billing support about it and try to get your PP/CC unblocked but other than that you will no longer be able to use them at all until
You take some sort of action.