The error is fixed with "disable-check-own-socket"
If someone is interested for next times, the log-file "gpg-agent.log" is on the path "C:\Users\<my user>\AppData\Local\VirtualStore\Program Files (x86)\Mozilla Thunderbird\".

I have created the file "gpg-agent.conf" in the path "C:\Users\<my user>\AppData\Roaming\gnupg\" with the following content:

Sorry, I haven't waited long enough.
It's happened again. After leaving Thunderbird open for a while, when consulting another encrypted email, the window asking for the password does not appear and does nothing.
I need Gpg4Win, I'm going back to Gpg4Win 2.3.4

I think it might be a cleanup problem.
If you uninstall Gpg4Win 2.3.4, restart the computer, and then install Gpgp4Win 3.0.0, everything works correctly.

It works correctly when installed and executed.
After a period of inactivity and with Thunderbird still open, it stops working.
With Gpg4Win 2.3.4 it works correctly.