If your JIRA Client returns "Compatibility error" message when you are trying to upload an issue, the first thing you need to check is JIRA Server URL specified in the connection.
The problem can be caused by using an alias address for your JIRA server or using "http://" address instead of "https://". In these cases JIRA server will redirects all requests, sent from JIRA Client to the alias address, to the main address. This will work most of the time, but may fail in case of upload.
Also, this will affect the performance as each request will be repeated.
So to avoid this, make sure you are using the main JIRA URL in your connection settings - the one that you see in the browser when you are logged in.