I've been using Yac Reader for two months and it worked without any problems. But for a few days now I've been having problems connecting to the server. My tablet connects to the server and after 5-10 seconds it disconnects and then connects and disconnects again. I can't even import a comic book to the library because after disconnecting I lose the progress of the downloaded file. I reinstalled the app on the tablet and the problem persists. The same thing happens on my phone. I'm attaching a recording of the tablet's screen with the problem.
Are you using your local network? Sounds like a network problem, try resetting your router, and check its logs in case something is going on with your router.
If your server is running some sort of firewall or AV program, do try fully "exiting" the program and trying again. (Disabling it may not work).
Your nick reminded me of Kaspersky and network issues with it. And even though I love Kaspersky, it's known to be notorious for creating network issues.
YACReader
