qBittorrent official forums

qBit has been working fine until recently when it stopped connecting to some trackers.  No changes were made to either the computer running qbit or to the router.  The tracker status for torrents that were previously seeding is now "not contacted yet", newly added torrents will have tracker status "working" but still do not download. The trackers themselves are up and running.  I tested an ubuntu iso torrent, it worked fine.  From my research I added "Advanced\AnnounceToAllTrackers=true" to qBittorrent.conf, and restarted the service.  I tried with default settings as well.  The ports I'm using are open, I tried disabling the firewall in Ubuntu in case it was changed without me knowing.  Still no luck. 

Ubuntu 18.04
qBittorrent-nox 4.1.1

Queueing is messed up in qBitTorrent and can cause torrents+trackers to not be attempted when they should.

Can you try disabling queueing completely? (Do be careful that it doesn't trigger qBT attempting 100+ torrents at once!)

Disabled queueing, but there is no change. Everything is still "Not Contacted Yet".

Enable everything in qBitTorrent's logger and look there for further ideas as to what's going wrong...

...because it sounds like qBT is bound to a "dead" network interface.

In the logs I found the most recent torrent I have added that did not download is having an I/O error, permission denied. The user that is running the qbittorrent service has permission for all the directories it is trying to write to. 

I'm not sure how to change what information is recorded in the logs.  The web ui has fewer options than the standard interface and I'm not sure what I'd have to add to the config file. 

I don't know how to enable log settings in the webui either.

But the I/O error, permission denied ...may be a transient thing, like an anti-virus scanner that locks files and "gets in the way" of qBT as a result.

Most likely permission denied is not qBitTorrent's fault, and it is worrisome that you do not know the cause...because file infector viruses/malware can cause that too!

There's also this report:
Torrent stalled with I/O error about an invalid handle    https://github.com/qbittorrent/qBittorrent/issues/9038
...so check qBT's github's issue list for possible causes.

Thanks for all the help.  I changed the owner of the directory from root (which it has always been) to the user running the qbit service.  Now it seems to be working again. What caused the issue is still unknown, but it if it returns I will update.