Just thought I'd jump in here: I have the exact same problem, using a Chase Saphire Reserve CC as well. My bank confirmed it's not on their end - they see the payment trying to go through, but that they're "redacted" (not the word they used, but something similar) on AirBnb's side before it even hits the bank. I have had this error before today (a few months ago), but figured that it would have been resolved by a competent company by now.
I am a developer and am looking at the error that's getting thrown:
error_code: 420
error_details: "Unable to perform action. Please try again through the website or contact support if you need immediate assistance."
error_message: "Unfortunately, a server error prevented your request from being completed. Airbnb may be undergoing maintenance or your connection may have timed out. Please try again."
Really seems like it's an internal error on AirBnb's part. It's really concerning that this has been an issue for some time and hasn't been resolved. Hope we get some assistance, and in the meantime I'll send in a bug report or something.