You must have changed the proxy settings in the Arduino IDE preferences since the last time the IDE was in a functional state. There is a bug in Arduino IDE (which should be fixed in the next release) that causes it to get an invalid configuration if you set the preferences to cause Arduino IDE to access the Internet through a proxy and then later change the preferences back to "No proxy".
I'll provide instructions you can follow to fix the configuration:
Select File > Quit from the Arduino IDE menus if it is running.
Delete the file at the following path:
C:\Users\<username>\.arduinoIDE\arduino-cli.yaml
(where <username> is your Windows username) Please be careful when deleting things from your computer. When in doubt, back up!
Start Arduino IDE.
Arduino IDE should now start up fully and be functional as usual.
Note that the file you deleted is also used to store other IDE preferences. These will all have been reset to the default values. If you had customized either the "Sketchbook location"
or "Additional Boards Manager URLs" preferences, you'll need to select File > Preferences from the Arduino IDE menus and then set those preferences once again.
Please let me know if you have any questions or problems while following those instructions.
Thank you so much. Your solution was easy to follow and worked first time. I honestly do not remember deleting any files as I am new to the Arduino IDE and have been very careful. I checked the preferences and the "no proxy" was already checked.
Thanks again
Warm regards
Please be careful when deleting things from your computer. When in doubt, back up!