There are many reasons a Outlook trigger wont find but I have found a common issues when promoting flows from Dev to Test.
The issue is caused by a quirk in how Microsoft has setup the trigger.
By default the trigger folder is set to 'Inbox', and when you peak the code you see the parameter is 'folderId' and the value is 'Inbox'.
But when you select a file through the folder picker the 'folderId' value becomes a GUID.
Selecting GUIDs through a display name is common is Power Automate and not particularly an issue, except in this case it is inconsistent. Because if you now select the Inbox from the folder picker the 'folderId' value is no longer 'Inbox', but a GUID, which is specific to this mailbox. Meaning it will not work when promoted to test with a different mailbox (as the Inbox has a different GUID, causing the trigger condition not to be met).
What's even worst is there is no visible way to see that trigger is using a GUID instead of path without peaking the code.
To fix it simply click into the 'Folder' input box, delete everything and then type 'Inbox' back in.
And this works not just for 'Inbox' but any folder, even custom ones. You can even do the same with sub folders, by adding the parent folder and a /
The key thing is to never use the folder picker, always type in the folder you want. That way you can transfer between mailboxes and it will continue to work.
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This is a series of short blogs designed to help find solutions for random problems before you ask, keep your eyes out for more
Fixing Redirect URLS: https://powerusers.microsoft.com/t5/Power-Automate-Community-Blog/1-Minute-Fixes-Handling-302-Redire...
Fixing Cant Call a Flow from a App: https://powerusers.microsoft.com/t5/Power-Automate-Community-Blog/One-Minute-Fixes-Can-t-Call-a-Flow...
Summing Up the Fields: https://powerusers.microsoft.com/t5/Power-Automate-Community-Blog/One-Minute-Fixes-Summing-up-a-fiel...
l also do long form and broader Power Platform blogs here https://dev.to/wyattdave