My Teamviewer 12 don't show GUI on Ubuntu 18.04.
$ teamviewer
Init...
CheckCPU: SSE2 support: yes
XRandRWait: No value set. Using default.
XRandRWait: Started by user.
Checking setup...
Launching TeamViewer ...
Launching TeamViewer GUI ...
... and nothing.
client.conf
[strng] FT_Start_Directories = ""
[int32] LastCorrectorRun = 1
[strng] Meeting_UserName = "xxx-xxx"