MKR Boards No Longer in Boards Manager

I've been using the MKR1000 for a couple years now. Today when I plugged it in, it did not show up as an option as a board. I got a pop up at the bottom saying that I needed to install the package to use the MKR. I clicked it and nothing showed up in the boards manager. I am very confused.

Hello!
And what version of the IDE are you using? Is this the most recent from this site? Or the previous one? And what platform are you running on?

Arduino IDE is 1.8.6
Mac OS 10.13.6

After you open Tools > Board > Boards Manager and wait for the downloads to finish, do you see any error messages in the black console window at the bottom of the Arduino IDE window?

pert:
After you open Tools > Board > Boards Manager and wait for the downloads to finish, do you see any error messages in the black console window at the bottom of the Arduino IDE window?

I get this one: http://downloads.arduino.cc/packages/package_index.json file signature verification failed. File ignored.
no protocol:

CLK:
I get this one: http://downloads.arduino.cc/packages/package_index.json file signature verification failed. File ignored.

Please do this:
This error indicates you need to take some drastic action. Be aware this is somewhat advanced and will remove any boards you have installed via Boards Manager:

  • In the Arduino IDE, click the link on the line following File > Preferences > More preferences can be edited directly in the file. This will open the Arduino15 (or similar name depending on OS) folder.
  • Delete all files under the Arduino15 folder except for preferences.txt. Please be very careful when deleting things from your computer. When in doubt, back up!
  • (In the Arduino IDE) Tools > Board > Boards Manager
  • Wait for the downloads to finish.

After doing that, does the "file signature verification failed" error still occur?

CLK:
no protocol:

This message is unrelated to the "file signature verification failed" error, but we can fix this too. Please do this:

  • File > Preferences
  • Click on the field to the right of "Additional Boards Manager URLs".
  • Press Ctrl + A. this will select the full contents of the field.
  • Press Ctrl + C. This will copy the selected text to the clipboard.
  • In a reply here on the forum, press Ctrl + V. This will paste the copied text.

Once I can see what you have set for "Additional Boards Manager URLs", I'll be able to understand the cause of the "no protocol:" and provide instructions for you to fix it.

For the MKR issue, it went back to normal for a little bit and then when I plugged in my MKR, all the options disappeared from the boards manager again. I then tried your suggestion and nothing changed.

pert:
Once I can see what you have set for "Additional Boards Manager URLs", I'll be able to understand the cause of the "no protocol:" and provide instructions for you to fix it.

https://git.oschina.net/dfrobot/FireBeetle-ESP32/raw/master/package_esp32_index.json
https://dl.espressif.com/dl/package_esp32_index.json
http://arduino.esp8266.com/stable/package_esp8266com_index.json

CLK:
For the MKR issue, it went back to normal for a little bit and then when I plugged in my MKR, all the options disappeared from the boards manager again. I then tried your suggestion and nothing changed.

It sounds like you're encountering this bug:

Please comment there with the HTTP headers for the following URLs:

as well as your geographic location.

CLK:
https://git.oschina.net/dfrobot/FireBeetle-ESP32/raw/master/package_esp32_index.json
https://dl.espressif.com/dl/package_esp32_index.json
http://arduino.esp8266.com/stable/package_esp8266com_index.json

I needed the text as shown in the Additional Boards Manager URLs input field directly in File > Preferences. The text you posted is from the expanded field you get when you click the button on the right side of that field and is useless to me for diagnosing your problem.

This is a screenshot of what I see. I don't know what other text you are referring to.

That's the text I need. It's a comma separated list. The text you posted is a newline separated list. The newline separated list is of no use to me.

CLK's picture: