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Do you have your emergency recovery key? You will need to use that if you can no longer access your old phone. If you have your old phone you can connect it to WiFi and you should be able to use the app to 2FA. https://confluence.atlassian.com/cloud/two-step-verification-976161185.html#:~:text=Disable%20two%2Dstep%20verification,-If%20you%20disable&text=You%20won't%20see%20this,click%20Disable%20two%2Dstep%20verification.
I do have an old phone but I wanted to switch my 2FA to my new phone since I won't be using my old phone. When I click on disable two-step verification. The error popup said something is wrong. It won't allow me to disable it so I can enable and scan the new 2FA from my new phone.
One last idea that comes to my mind is to see if a different browser also brings up an error message when trying to disable 2FA or to wait a few hours if there has been a system error on cloud probably.
As you do not have some sort of log files, unfortunately nor do we have, best option like Brant mentioned would be to raise a support request with Atlassian support.
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