Which Teltonika hardware are you using ? In most of them, there is a feature called DOUT Control Via Ignition.
If you use this feature for your used case, You can't use ignition for the normal use.
First configure Digital input 1 as your ignition source in system settings.
In Features, DOUT Control Via Ignition settings,
Enable DOUT1 in DOUT control
Enable DIN1 in DOUT Deactivation via DIN.
Set Ignition off timeout as Zero.
By using Normally Close (NC) contact of the door senor, Give VCC to Digital Input 1.
So when you open the door,the ignition will turn off and the Digital Output will turn ON.
Thanks in advance