LBS
What makes you think it's a server issue?
You should, if the device sends a position to the server with a invalid flag (you can see and check it in the traccar server log for the device).
If the device sends a position marked as invalid then traccar server request the location from a geolocation server (when the device reports wifi / base station info).
Ps. Why dont you translate you message with google translate to English. This is more helpfull to get replies.
Salut a chaque fois que mon tracker pert le signale GPS il arrive pas a donner de position au serveur par LBS. Que faire dans ce cas