Older versions of Teamviewer are being phased out by the Teamviewer company from September 15th 2021. The advice on the website suggests you need to upgrade to version 15. However, v15 is not compatible with the older Windows XP machines in the field.
The latest XP compatible downloadable version of the Host program is 13.2 and is available here
Regrettably, the update process on older versions is not simple, and frustratingly cannot be done remotely. It needs intervention from an operator at the machine with a small amount of technical know-how
Étape 1 - Stop the running Teamviewer Host Program
Right click on the teamviewer icon in the taskbar (bottom right of screen)
Select Exit Teamviewer
Étape 2 - Uninstall the old version of teamviewer
Go to Control Panel->Programs and features
Find Teamviewer Host
Uninstall it, but do not tick the box that says "Remove all settings"
...Keeping the settings means that the PC will keep the same teamviewer id
Étape 3 - Download and run the new teamviewer host install