It seems to work ok, just confusing because it requires placing a donation amount in the 'Amount' field, which is not how PP donation usually works. Looks like the old 1.1.x donations mod. If you use the PP donation code, it works like this -
The amount is entered on the PP donation page, that's what people are accustomed to.
You are currently running 1.1.21. Suggest you upgrade to 2.0.10 and use the Paid Subs feature, which is core in 2.0.x. It allows you to restrict access to specified areas only to members who have subscribed, by assigning them to a privileged membergroup. If you prefer to stay with 1.1.21, you can remove the mod and just use the PP code. That's how it's set up here