Does anyone have an answer for this? It is tiresome to have to reach behind the computer unplug the USB and then plug it back in. Mostly happens with these ESP8266 gadgets. There are a few other spurious messages that can happen and the answer is the same for those too, unplug, replug.
Push the reset button on the board? Some ESP boards require a pin to be held low, to perform programming. Some have a circuit on board to do that, but it sometimes needs a little help. But you didn't tell us what board you have. Read the sticky threads at the top of the forum to find out how to ask a question.
Also, please edit the strange thread title to express the question that you are actually asking! That is covered in the instructions as well...
I tried to fix it. if it was all the time that would be one thing, but this is only after it's been connected to my computer for a few hours. prior to that it's ok.