Hi,
What version of Office did you use?
Did you mean the phone authenticate to sign in account?
If you're using Office 2021 LSTC, you don't need to sign in the account with phone authenticate.
If you're using personal account, you need to set it up yourself about how to verify your account.
If you're using organization account, you should contact admin to confirm if you need to phone authenticate.
If my understanding is incorrect or you need more help about this problem, please be a bit more precise to explain your requirement so that I can get more accurate solutions to this problem. I’m glad to help and follow up your reply.
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