Description of the issue
Your MYOB company data file is hosted in your own network, not in the cloud, and you can no longer access any of the local MYOB data files from the integration application, and you recently upgraded MYOB AccountRight to version 2021.1.
Explanation
Starting on version 2021.1 of MYOB AccountRight, you will need to use the MYOB AccountRight AddOn Connector.
Solution
Close the integration tool if it's open.
In your Program Files, find the new MYOB AccountRight AddOnConnector item on the menu and open it.
This will launch the AddOn and you will see a confirmation box like this:
Make sure the box to run it at startup is ticked, that way it will launch automatically next time you start up Windows. Click the Close button.
Launch the the integration tool and you should now be able to connect to the MYOB data files.