Yesterday, my Facebook, LinkedIn and Twitter integrations in Internet Accounts all started prompting for a password. When I filled in the correct password for each account, none of the accounts would take the password. I went to each individual site and manually filled in the passwords. They all worked. After about an hour of getting really annoyed, I decided to try logging in using Internet Accounts on a Mac that is not mine, and is not associated with my iCloud account, which leaves out this being an iCloud Keychain issue. The same thing happened on the other Mac. If I removed the accounts, Facebook and Twitter appeared to work at first, and then they started nagging me for my password again. LinkedIn gives a very strange error. Instead of giving me a specific error, it instead shows me a very long URL in red text that cannot be copied, so to try the URL, I had to manually type it in a web browser. Doing that accomplished nothing. I spoke to AppleCare about it yesterday. If this is something that is known at Apple, the AppleCare people don't seem to know anything about it. Has anyone else seen this? Both of my Macs are running macOS High Sierra 10.13.4. The other Mac I tried this on is running Sierra 10.12.6.