Synchronization is blocked if attachments are synced to a Windows Server.
If you use a Windows Server to host your Jira Server instance, then the problem might be caused by the special characters in the connection name.
Windows has a set of characters that are not allowed for file names in the system. More details.
Update the connection name via database query on both sides
For Jira Server and HP QC/ALM
- XXX is the name of connection
- YYY the connection id