Reset the device (setting new device for the user)

I’m trying to solve some problems with this plugin for a friend of mine. I’m not the person who made initial setup (long story – it was her sone & now they’re not on speaking terms).

Situation 1
My friend, it’s her site & she’s got admin access, she changed her computer. She ended up creating new admin because the could not login with her old username-password.

Situation 2
Now, there is a client who failed to login and who doesn’t answer on who it looks like when she fail. I suspect that it’s the same story, she probably changed the device.

Question
Is there anyway to “reset the device” manually, so the user could login again and plugin would remember this access afresh.

PS
Sorry, I probably call it wrong way that’s why I could not find the answer in search…