me: [painstakingly copies entire .firefox folder from other machine]
Firefox: Hi, welcome to your new setup! Wanna import settings from somewhere?
me: Uh, you don't see the ones that are already there? Then ok, I guess so... import, plz.
Firefox: No programs that contain bookmarks, history or password data could be found.
Me: You didn't exactly ask me where to look for them. How about asking? Cuz all the data is literally in your profile folder right now.

This always happens. I think it's probably part of the scam to get everyone to sign up for Firefox Sync, which I refuse to use on principle since they now force you to connect to their server instead of allowing 3rd-party servers.

#softwareGripe

@woozle I can't say this has ever happened to me and I have done it literally hundreds of times on Windows machines, and a few on MacOS and Linux. Maybe you're missing a step?

@bthylafh What other step can there be?

@bthylafh Afterthought: does it not like the folder being a link? I'd have been suspicious of that, except that's the way I have it set up on the source machine too, with no problems.

@woozle Could be. I don't ever make it a link. My process is (on Windows) copying %APPDATA%\Mozilla to the new user folder in the same position and Firefox finds it every time. This method preserves the random profile folder names as well.