First time I’ve used the Freestyle Libre and it is hopeless. It stayed on my arm for 90 minutes then fell off - it cannot then be reapplied so that was £50 of NHS money down the drain. What a waste of time !!!
If you look through the forum you will find lots of tips on how to improve your chances of the sensor staying on.
For my first two I was cautious and put a strip of Kinesiology tape over the sensor. For this one I am trying an arm band but I may be getting an allergic reaction to the material.
I assume that you followed the instructions and cleaned the site with the wipes then let it dry thoroughly.
It might help if you can get someone else to work the applicator. I haven't quite worked out yet how to get a reliable strong push underneath my arm.