Error when I try to buy a campaign - Sandbox API available?

I’m trying to use the Patreon API to develop a backend application. Initially everything was working fine, but now I have a problem, because they blocked my account.
I tried to create two fake accounts. Say, user A and user B.
User A would be the creator, while user B would be A’s patron.
I can even create the accounts, but unfortunately I am not able to become a patron of B, because when I try to buy the campaign, I get a permission error like this:

I would like to know if there is any way around this problem, or if there is any sandbox that I can use to test my integration with my backend.

Thanks in advance.

You can try keeping the creator and test accounts separate.