Hi,
I am using my old Win 10 computer to 3dprint, Arduinos, and all this diy stuff.
All Windows updates are done.
IDE 1.8.19 was ok until a couple of days. Now I got an issue.
The IDE icon is visible on the task bar, but the window doesn't open.
The name of the last .ino file is attached to the icon window on the task bar.
I do a fresh install without success.
Any idea ?
Welcome back
Lets see what happens behind the scene:
If you're using a multiple monitor setup the IDE might be running in the other monitor. If that monitor is not connected you will not see the IDE.
If that is the case you can take the following steps.
You can practice with a visible application.
@ledsyn, OP is using IDE 1.x, not 2.x 
So no output? There gotta be at least a log file somewhere.
But the idea it might be on another monitor is clever, it happens.
For the 1.x series there is arduino_debug.exe in the same directory as the arduino.exe; intended for debugging purposes.
It however is a different application from arduino.exe and if it did not run in the past on a different monitor it will start on the default monitor.
Ok, so it's not dependent upon the sketch, i.e to open a new sketch will also (not) show up, on the other monitor.
I am covering my head with ashes 
After spending hours and a great part of the night on this issue, it wasn't one.
At last, I right click on the IDE icon on the task bar ... and find left click to expand it.
I don't know how the IDE window became so small that it was not visible on the screen !
I am sorry because it is ridiculous but thank you all for helping me.