I work for the IT team of a mid-sized company, and we use Teamviewer 12 extensively to connect to remote users.
I have noticed an issue over the past 2-3 months involving only users that are running OS X.
They all have the same ID: [ID removed by moderator]
This was odd to me at first, but I started noticing I could never connect to any of them, from a Windows machine or a Mac. When you type in the ID and hit connect, 3/4 times it will go to authenticating, not show a password field, and go right back like you never hit connect. When it finally pops the password field, it always says incorrect password, no matter what.
This is becoming increasingly frusterating as we are having to send all of our remote users links to Teamviewer QuickSupport, which somehow works flawlessly. Most users are not completely technically savvy and are confused and annoyed when Teamviewer doesn't work properly and it is reflecting badly on us.