So I will move my post here:
Perhabs the packet got some serious shock and the load cells or some mechanical part got damaged?
My only guess is it's failing to self-calibrate at boot and hanging there.
What's this plastic thing? Seems like a locking mechanism to prevent damage on shipping?
I know some scales have some locking method to prevent damage on shipping, so have look around it, and check the manual if you have it!
Have you tried rotating it so the notch aligns with the lever?

Did you transport them or was it bought online or something like that?
If you did it without locking them, they probably got damaged