Cannot Purchase Pro Plan


I’ve been having some issue with a few websites on my account it doesn’t seem possible to purchase a Pro plan.

From the Overview page I click ‘Change’ next to ‘Free Plan’, then choose ‘Pro’ and continue.
The subscription confirmation box appears (all information is shown and the card is correct) and I click ‘Purchase’.
The pop-up box from underneath confirms that the plan was purchased, but when the tab is refreshed, it goes back to the Free plan.

This issue is the same as this topic: Problems to change to pro plan which was closed without a response.