Found a solution elsewhere on the forum! 

Hello! I have a similar situation (Windows 7, IE11). How did you solve this problem?

I used the instructions in the second post in this thread: https://www.eventideaudio.com/community/forum/stompboxes/cant-purchase-algorithms-through-paypal-through-h9-control

“To those who come across the same issue, follow these steps:

 

1) In the paypal window, right click and select properties.

2) Copy the URL of the page

3) Paste the URL into a new browser window.

4) Complete PayPal transaction

5) In the H9 Control, in Settings, click on Restore Purchases.

 

After this, the new algorithms are available in your H9 control. ” 

I did this in Chrome, I believe… but it was almost a month ago now. 

Good luck!