Thanks for reaching out. We do have an option to create and share reusable assets and also you can link assets from the master source. For more information on that you can refer to this help article: https://helpx.adobe.com/in/xd/help/linked-assets.html
If you are still unable to link the assets, I'd request if you can try creating a new file, copy all the contents and then invite everyone to that file and see if that works.
We tried creating a new file but the problem with that is that the files already created using assets from the "old" file don't recognize the assets from the new file as the same ones because I'm sure they have different IDs in the code background. We don't want our designers to have to take the amount of time needed to link everything to the new document assets only to have it fail again.
I did find a solution and posted it below. The issue is that the "master" file goes "out of sync".
I found what was causing the issue. The "master" file keeps losing it's "sync".
If the owner of the "master" goes to the gear icon in CC Desktop and selects "Syncing" then pauses the syncing and restarts it, the files other developers have created will then start seeing the changes to the Assets. We are having the lead designer that owns the file do this stop/start resync weekly or sooner if the sync stops.
Nice to hear that you are able to find the solution which was causing the trouble. Please feel free to reach out to us in the future for any query related to XD.
We'd be happy to help.
Is there a way to access the design files if the master document belongs to someone who has been unresponsive? I have a client that doesn't have access to their design files because their original designer never shared anything beyond the developer share link & the designer is not being responsive.