Of course, this should not happen. So far, all payments have been successful. We will remove the error as soon as possible. Can you please send me your BCH address and we will transfer the amount to you again.
I kept the browser open, tried again, and
it worked now. It added 5.5 hours to my VPN.
Everything worked in Tor browser, without captcha.
10 sat vB looks fine for me... it is likes that for a month already.
You can't pay $1 per transaction to send $0.05.
@Donald_Buck: you should probably start your topic with this:
The project is not a student project, but takes place as part of research work on the topic of crowdsourcing at the University of Stuttgart.