Try repositioning it. If you're below it's threshold detection level not much else to do.
I haven't play with these as I'm aware of my h/r and bp is mostly irrelevant to me. The O2 saturation be interesting to monitor if accurate though.
It's all mostly a curiosity to me and serves me no practical purpose as I've always trained old school.
Well if it doesn't grab in a minute I would expect your bp and volume levels to drop even lower.
You sitting or lying down?
Even sitting ramps bp up considerably.
When your feet/hips/chest/head are level your bp will ramp down to its lowest level.
Remember that if you have a bleeder or head trauma as it can save your life.
Works well with bad nose bleeds too, lol.