Did you end up getting that tax issue answered/fixed? I've been waiting on a reply from support regarding that issue for 3 weeks, but no response to my email yet.
Edit: let me clarify to see if we're running into the same issue. The first reply I got when I asked about this issue on July 1st is
"Thanks for reaching out. We recently made a change which defers the tax validation process which may detect the final withholding rate.
You final withholding rate will be available by the time you are requesting a payout.
If the issue persists and you need to retake the tax interview, you can do so through the following link:
https://itch.io/user/settings/seller/tax-information?retake
Thank you, let us know if you need further assistance."
I already retook the tax interview just before reaching out to support, I think (I filled it in twice anyway). I read the email and understood it as, "it might take a while to show up, wait until you can request your payouts". Which I did, but on July 8th the tax rate was still at 30%, at which time I sent a second email (no reply).
I just filled it in a third time, getting the confirmation that my tax withholding rate should be 0% IN the interview, but the issue persists.
Edit 2: Just figured this out, but replying here in case anyone wants to search for this on the forums. The "available for payout" amount reflected the 30% tax rate amount. But once I requested a payout, something seemed to click in the system and the warning is now gone in the tax info tab, and the actual payout reflects the 0% withholding rate.