I was facing Authentication failed issues when accessing flow for first time in my
Office 365 developer account.

so i followed the following blog

https://flow.microsoft.com/en-us/blog/known-issue-login-troubles/

but was not able to resolve, so i decided to open ticket with MS.

To cut this story short, do the following

• At the Step 4 in the above blog, select “Microsoft Application” and  paste “7df0a125-d3be-4c96-aa54-591f83ff541c”, remove any spaces when copy/paste this GUID
• then you can see Microsoft Flow option, but for me it wasn’t redirecting when clicking.
• So I open the Link in Chrome “incognito” mode,(asked by MS Support to do so), now it was clickable
• now you can proceed and perform all the remaining steps.

Regards,

Shakir