I also had the same issues with two sensors in a row too started the sensors Libra 2 on my iPhone as stated following all directions and my app said that I had to start my sensor on my i phone to make it able to have alarms ……
I found it really frustrating began to wonder if I was going crazy as I always use my i phone to start the sensors not my blue reader . However I think we should be able to use the reader along side the i phone as our phones can run out of battery and then you need to take a whole blood test to find out what your blood sugar is doing it would be more practical to have both working properly . I am an older lady and have been using the libra sensors since they were first brought out self funded until nice put them on prescription. I think that these teething issues should have been fixed by now at present with my current sensor I find that it won’t always talk to my phone . I always carry my phone in my pocket in range of my sensor and charges it each night to stop any issues occurring. When I sleep my phone is on charge next to my bed about 2 feet away from the sensor on my arm . It still often won’t register any readings when it’s supposed to . I am awake often as my mum has dementia and her alarm goes off and I check her . At the same time I take a reading scanning my sensor , because the. Sensor hasn’t worked properly I suddenly get a high blood sugar warning a minute after which is annoying . I would have taken the insulin earlier to counter act the rise in blood sugar if the app was communicating properly . It’s not us it’s the tech that has the issues not sure what can be done about this problem I think out of the last half dozen sensors I’ve had at least 1/2 of them not communicating with my phone correctly . My husband who is an electronic engineer and deals with software design and computers has told be it’s the sensors that are not working correctly due to the software on the app . I usually wait until I start up a new sensor and hope that it works properly but having seen your post I will be getting a replacement for the faulty sensors from now on .