Sim800l can not keeping sending data to my mysql database

Hello ,
i have a sim800l v2.0 module it was sending data to my MYSQL for more than 3 hours . but it reaches a point where it does not send and there is an led that is flashing about 8 to 9times and then stop by getting OFF and restart again.
i checked the power which i think is good.
battery 3.7*4 V , 6000mah and PV which keep the battery powered
DC to DC adjustable Module used.
and this is my second sim800l and i had the same situation. what is you advice.
thank you for supporting the community.