"Someone has already set up Teams for your organization"

dbrower256 - So we believe we've found the issue. If you can confirm the scenario above then that would be great. Here's an article which references the issue: https://support.microsoft.com/en-us/help/12407  ("I want to use a different email address or phone number to sign in"). The issue here is that your account is tied to both a work & personal account, so in order Teams sign-in flow to work, you'll need to 'de-link' these accounts with the steps in the article. 

Thanks,

Sam

PM, Teams Engineering