Device disconnecting from mqtt every 60 seconds

I'm having trouble with the MQTT client on esp8266. It can't keep a connection alive.
any help!

I am not sure which library you are using and I use different boards and the ArduinoMqttLibrary running MQTT for a long time. The WiFiSimpleSender example of the ArduinoMqttLibrary has the following line with comment.

void loop() {
  // call poll() regularly to allow the library to send MQTT keep alives which
  // avoids being disconnected by the broker
  mqttClient.poll();
...

Do you have something similar in your code?