This could mean anything: an incorrect/outdated server configuration, a local Qt issue, … We need more information. Please tell us how you installed the client. Also, a log file might reveal more detailed information, so please provide one.
No. Please delete it, it is publicly accessible and contains personal data.
You need to enable logging in the settings, as mentioned in my previous post. Open the client settings, go to “Log settings” and enable logging to a temporary directory. The user interface will tell you the exact path.