LimiTTer return zeros

Hi, 
the program is returning 62C2000.... for the first value of "str" and 0.00 for the "Glucose level" and "15 minutes-trend: ". i wonder if there is any problem with the activation of the sensor because  i dont have the reader and play store don't allow me to download "liberlink". 
Any idea to fix this problem?

Thanks !