I have torrent file without trackers.
uTorrent found ~70 peers after 30 minutes
transmission-daemon found 0 peers
What is wrong with it ?
udp/tcp ports open for both clients, dht also enabled on both clients
If your two clients are on different machines...
First think to check for is leakage - TCP + UDP + uPNP.
If any of these packets are leaking, then various upstream providers in your ISP chain will block your connection.
If you find leakage + close it, then eventually your connections will establish again... usually... Sometimes ISP leave this type of block in place permanently. It your connection doesn't re-establish, say in 30-60 days, then you may have to change ISPs.
Best approach is to use a VPN on any machine using any type of torrent protocol. Whether you're pirating content or doing legal downloads or providing seeding for code or data you've generated.
Just try explaining you're seeding LibreOffice to help with their project or you're delivering your own video course via torrent. There's no way for upstream ISPs to differentiate legal + illegal torrent usage.
Any leakage will likely cause a connection shutdown, unless you use a VPN.
If your two clients are on the same machine...
Use tshark or your OS equivalent to check packet flow to determine where problem is occurring.