The 5511 error code changes made to your data online have been downloaded but an error occurred while making these changes to your QuickBooks company file. The main cause of the error could be happening because this company file was not open in QuickBooks during Sync Manager set up.
For resolving this QuickBooks error it is very important to check if the Intuit Sync Manager is registered as an Integrated Application in QuickBooks:
Open your company file in QuickBooks software
Choose Edit – Preferences, and select Integrated Applications
Click the Company Preferences tab and see if there is a checkmark next to Intuit Sync Manager in the list
If it is not checked, click Sync Now in Intuit Sync Manager while the company file is still open
Also ensure you have the latest Intuit Sync Manager update.
If the above mentioned solution does not resolve the issue or answer your question, you can read discussions and post messages and questions relating to your issue on the Intuit QuickBooks Error Support introduced by Intuit or you can connect with the QuickBooks technical support for guidance and error fixation.