When working with Postman in an offline mode or not signed in, then choosing to sign in, you lose access to your Collections and Environments you have worked on previously.
In later versions, Postman introduce the Scratchpad. This is an offline area where your data is saved to.
When you create a new account in the app, you should be presented an option to move your data from your scratchpad.
If you already have an account to log into, you do not seem to get this option.
- Within Postman application > Click the Settings Cog > Select “Scratch Pad”
So now you should be able to see your offline data. If you can, you need to manually export your data then change back to your workspace and import the data.
If you are still unable to find your data. I recommend you follow this article from the Postman support site on “how to recover my data”. I did not personally have much success with this method.