Virtual write

i am trying to make a temperature read
when i write this code, the device say “particle photon is offline”.
and it happens because of the last line
int sensorValue = analogRead(A0);
float volt = (sensorValue/1024.0) * 5;
int tempC = (volt - 0.5) * 100;
Blynk.virtualWrite(0, tempC);

any help with that please?

That doesn’t look like you have posted the full code?