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Disconnect after a few minutes or no connect at all

I have a project on an ESP8266. With the latest Blynk version on the new Blynk IoT app. Unfortunately the controller disconnects after a few minutes and does not reconnect. I have already tried my controller in another network and there I do not have the problem. Are there any ports or similar that I need to enable in the router?
The Ip of the ESP is not assigned twice, that I have checked.

Post your whole sketch please

Also post your serial monitor output from boot-up to disconnection.

Pete.