hey, yikes sorry you ran into trouble right away!
First, make sure you toggle guardian on/off so the floor is set correctly.
When you launch the app and see the "welcome back" , click down on the left thumbstick button and hold it. You'll feel a haptic bump , just wait about 7 seconds and it'll reset everything. Or you can just switch to a different profile using the buttons on your left wrist.
There is a "set floor height" button in options, it is useful to guarantee that your floor is correct every time you load back in (if you end up way too high above the floor)
Lemme know if you run into more issues.