Went through this exact nightmare a few months back before an exam too, so I know how stressful it gets when it's this close to the date.
A few things that actually helped when I was stuck:
First, don't keep creating new accounts if the login is failing. It feels like a workaround but it usually makes things worse on their end, since support then has multiple account IDs tied to your name/email and it gets harder for them to track which one is the "real" one to fix.
Second, if you're getting the "too many password reset requests" lockout, stop trying to reset for a bit. Each failed attempt seems to restart that 30 minute cooldown, so spamming it just keeps resetting the timer instead of getting you in faster.
Third, and this is the annoying part, Databricks support genuinely cannot fix Webassessor/Kryterion account issues directly since it's a separate vendor. What worked for me was filing a ticket through the official Databricks help center link (help.databricks.com) rather than posting only here, and specifically asking them to escalate to Kryterion with my login ID/email attached. Community replies here are monitored by their cert team, but actual account fixes only happen through that ticket path, not through forum replies.
If your exam date has already passed because of this, mention that clearly in the ticket and ask for the voucher/coupon to be reinstated due to a platform side authentication failure, not a no show. A few people in threads like this did get their exam restored after pushing on that point directly, so it's worth clearly stating it wasn't a user error.
Rough experience, but posting your log ID in the ticket (not here publicly) usually speeds things up more than repeating the issue in the forum.