Below are the possible main reasons of device offline, we also provide checking way accordingly. 1.Power supply Some drivers like to turn off the battery of vehicle during parking, or the power wire connection between tracker and vehicle's power is disconnected (including be cut off by someone) Checking the latest online data like external power and internal battery value before offline will get clear answer to this question. 2. SIM card without available credit It is very common and is the main reason of device offline. However, the common mistake is that users think the SIM card has enough credit but actually the credit has run out. - The device can reply SMS command doesn't mean the credit is enough: Device online needs the GPRS data plan. Part operators provide different packages to their customers. For example, calling and SMS are one package, the GPRS data is another package. It is logical that the device can reply SMS or the calling is normal but the GPRS data has run out. - If the users use the M2M SIM card management platform, the situation is more complicated. The user can limit the data consumption of the SIM card. There are active/inactive SIM card, prepaid or postpaid options. Even everything looks normal, the M2M SIM card itself may have issues, especially under roaming network. The challenge is that the GPS tracker supplier doesn't have a reliable way to judge the SIM card credit. So the users need to keep a good record of SIM card recharging. Two further steps are suggested below: - Try to recharging SIM card if can't find other reasons of device offline - Replacing with another proved SIM card for comparison testing 3. Parameters are wrong IP, port, APN, and the time interval are core parameters affecting the online. We developed SMS command below to retrieve current parameters. 000000,C06 (000000 is default SMS command password) Below is an example of 000000,C06 reply C06,862273048221154,188.8.131.52:10502,TCP;APN:Etisalat,,, EXT:12.72V,BAT:3.94V;B03:10,0,0,ACC OFF,Stop According to the SMS reply you can know if the parameters are wrong About the APN, if you know the SIM card operator, you can Google out their APN. Normally each operator has own APN. Most operators only have APN, but part operators have APN, APN name, and APN password.