When somebody tries to sign in remotely, it says, that I have an old version of teamviewer installed.
@dariukas Indeed, the use of the free TeamViewer license is only possible with the latest version of TeamViewer on both sides of the connection.
You will find all the information you need in our Knowledge Base article here: Enjoy using the best version of TeamViewer we made so far! - How to proceed?
The use of previous versions will require a professional license.