As some outdated operating systems are not compatible with TeamViewer 14, you may not be able to use TeamViewer any longer on these specific devices.
This is something we carefully considered, and we took a keen look at the numbers before making this decision. In any case, the few operating systems that are not supporting TeamViewer 14 are not even supported by the manufacturer itself for a long time.
According to Apple's support page, you are still able to update your OS from Snow Leopard for free to El Capitan. This would allow you to continue using TeamViewer also on this device.