We ran into this issue today. At my network we block all traffic not originating from within the US. Our helpdesk was able to connect the day before. Ran a trace route found the *.teamviewer.com site was running through Microsoft Azure. That being the case we started adding country code one by one based off of Azure Data Center locations. When we got to Hong Kong teamviewer started working again. Bottom line was we had to trace out what country the teamviewer traffic was routing, allow said country, and got resolution. Obviously for businesses that block by country codes this is not an ideal solution and poses a security risk.
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