Suddenly cannot npm install using node-sass 4.7.2 / node 6.9.2

[Awbelton]

Using node 6.9.2, npm 6.13.4 and node-sass 4.7.2. Everything worked fine a few days ago, now I hit this snag:

npm ERR! code ETARGET
npm ERR! notarget No matching version found for semver@~5.3.0.
npm ERR! notarget In most cases you or one of your dependencies are requesting
npm ERR! notarget a package version that doesn't exist.
npm ERR! notarget
npm ERR! notarget It was specified as a dependency of 'node-gyp'

I've tried everything at this point, but to no avail.

[xzyfer]

@Rc85 you have a permission issue writing to /opt/portfolio/node_modules/node-sass/vendor. Check your permissions or try running npm install --unsafe-perms.

[xzyfer]

@Awbelton this is not a node-sass issue. Might be an node-gyp issue.

No matching version found for semver@~5.3.0.
...
It was specified as a dependency of 'node-gyp'