If it does give the message Wait and retest, then do that until it actually does say Remove and Replace. Sensors often will recover from initial insertion trauma around the filament head.
Failure to detect is something entirely different.
Are you just using an Abbott reader? The phone app can give this problem for a number of reasons. The reader will only give readings from a particular sensor that has been started from that particular reader.
If a reader just does not interact at all to the sensor, try resetting that reader. Make sure it is fully charged, then hold the button down for a full 30 seconds and it will do a soft restart without loosing and data.
One way to possibly detect a faulty reader is if you have an old sensor - does it detect that and say replace?
If none of that works, contact Abbott. It could mean something needs to be replaced but no sure way to tell which. You can start with a phone app but then no reader will work with that sensor.