I imported a schedule from P6 and received a warning message like this:
Warning: could not create link to the task [Install Cable Tray - Filter]. A task is located in another Primavera P6 project
Can I import multiple interlinked projects from P6?

This warning appears when there are links to a task that has not yet been imported to Synchro and the link cannot be created (as there is nothing to link to yet).  This happens when there are multiple projects in P6 with links between them.

1. Continue to import the remaining interlinked projects.
2. After importing all projects, for any projects that produced these warnings, Synchronise From the original file making sure to choose Integrate wherever available.
Important: Do NOT use the Synchronise option for Tasks when multiple projects are imported to Synchro as this will erase the other projects.
3. The settings below should be used to update the missing links.

 

4. After integrating, the synchronization report should not show any of these warnings.
5. Repeat this process to Synchronise From for all projects.  Now all the links have been created between projects.