Steam achievements in Unreal Engine projects (2 questions)

I got Steam achievements up and running (I can earn them in the viewport). But:

When I test in the viewport to make sure my achievements are working, I can trigger them, but only once. What’s that about? How can I reset them so they trigger every time (so I can repeatedly ensure they’re still working)?

Also, after packaging–is there any way to see the Steam overlay or test achievements? I try my packaged build and can’t access Steam through it (even with the .txt file containing my game’s app ID). Is overlay/achievement testing available exclusively in the editor and, eventually, once the game is properly uploaded to Steam?