Thank you for reporting!
This is weird. Unfortunately, I can't reproduce this. According to the logs, our payment provider didn't have any downtime recently. There's no Java in the payment widget, so it's not the culprit for sure. It's just an iframe that loads a page from the server of our payment provider.
I may guess that something blocks 3rd party widgets on the client side. Do you use any browser plugins or software that block offsite resources? Like adblock, privacy badger, firewall or something similar. Depending on the configuration, they may block everything coming from other domains. If it's not the case, then probably our payment provider did have unregistered downtime but now they fixed whatever caused it.
Sorry for the inconveniece!