Local blynk server disconnection form router and never recover

Hi , first thank you guys , this forum is very helpful .
i have a working server on pi 1.2 b , no issues here

i run a test lsat night , the sever was running over night without app blynk connected or something else .
the pi disconnect from wifi and never recover .
which file do i need to edit to stop that ( i guess is something wrong with the rasp wifi something manager connection ??

thank you