diagnose and heal
When I use Vuze, My NAT shows green & OK but then I check Network Status and I get Test failed: NAT test failed: No route to host (...:etc)
Check your port forwarding for TCP ***
I fix it by checking/changing the above TCP port, then it wigs some time later and I have to repeat fixing.
I wish there was an easier way to fix this problem with diagnostic feature that provide clear solutions that sticks.

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techguru commented
this is probably not vuze..this is either your pc...or your router/modem...it could have some NAT bugs in its firmware...if you have both a modem and a router...get the modem into bridge mode..and get a better router
if you have a combo unit...could try getting a different one