Are you able to install jsupm_buzzer after flashing the board?
The error log says "This is most likely not a problem with npm itself and is related to network connectivity." So the issue might be with in your network. Check your DNS in /etc/resolv.conf
When you have this issue, do you try to access the websites with your PC's browser? I'm asking because in this moment the website https://registry.npmjs.org/jsupm_buzzer is not available so if the websites are not working you will have some issues.
After flashing the board I am not able to install jsupm_buzzer. But that's actually my fault! It appears that jsup_buzzer is not in the npm registry! So I was incorrect in my post above that it is a valid npm library. Sorry about that. However, I have seen this issue many times for valid npm libraries, where the only fix that worked was to flash the board and then retrying npm install on that library. I'll try to post an error when it happens agaien. Lastly, for what it's worth, jsupm_buzzer seems to load fine with require("jsup_buzzer") without any npm install.