During the add-on startup, you can see the following message:
This error is an SAP Bug (Note: https://launchpad.support.sap.com/#/notes/2875011)
Workaround (from SAP):
End all SAP Business One Client-related processes (SAP Business One.exe and SAPbouiCOM.exe) and restart SAP Business One Client.
If the workaround doesn't fix the issue and it's persistent, please contact SAP support as this is an issue with the SAP environment.
There are a few things we know that can help:
1. Run the client in "Run as administrator" mode. If this helps, then there's something wrong with the permissions on the system as the UI-API cannot run while starting the B1 Client without administrative permissions.
2. The SAP B1 Client components are not registered correctly, or the installation has been corrupted. In that case, please follow our reinstallation guide to install the SAP B1 client properly.