I don't know what else to suggest because this is all I had to do earlier this week to fix the same problem but the commercial trial I had installed as for v11 and I was running the freeware v12 afterwards. This is on Win10 Pro 64-bit Creator's Update on a domain.
For Windows, delete all the previous TeamViewer config info in %appdata% etc that are left behind even after an official uninstall. If you can't see hidden files, use something like voidtools.com's Everything. Then you can reinstall the Free version.
Hi, You have to scour the HD and delete it of the previous config files. I use voidtools.com's Everything tool to find the TeamVewer stuff in %appdata% before reinstalling the free version.