I have steps that should help many with this issue get connected again. I hit this on my personal Azure pay-as-you-go account where I now have to login as a different username to get to my Databricks Account.

• In Azure Portal, go to Azure Entra ID resource and see which users exist. For me the admin user I normally log in with doesn't show exactly, instead a similar username with #ext# in it shows up.
• If there is an #ext# user that is similar to what you log in as, go to portal.azure.com on a fresh browser session (such as incognito browsing) and try logging in with that full username (should include #ext#).
• You may need to reset password to get logged in as this user.
• After you get that working, go to Databricks Account login at accounts.azuredatabricks.net and login with the #EXT# email.

See images below of how my typical username which I logged in with to Databricks (training@dustinvannoy.com) is no longer showing up in Microsoft Entra ID, but I now have the #ext# user (training_dustinvannoy.com#EXT#@trainingdustinvannoy.onmicrosoft.com) which has those important Azure admin permissions and I can use to login to accounts.azuredatabricks.net.