Mac OS 10.6 5-minute limit?

My elderly father has an old MAC which has an operating system updated to  OSX 10.6. The hardware will not accept a more up to date version. When we updated TeamViewer to the latest version (14) on his computer the other day (as instructed), we found that the programme throws us off after 5 minutes, as it claims (on my computer) that his has not been updated. Yet his computer says TeamViewer IS up to date. So we are stuck with the new restriction of 5 minutes.

I assume this is due to his dated OS. Is there any way round this so that we can continue to use TeamViewer (besides getting him a new MAC, which I fear might be too difficult to learn to use)?