Some music on Vault 2 not shown on Roon

I have my music stored on Vault 2. For some reasons about 30% of my albums don’t show on Roon although I can see them on Bluesound? No common thread such as artist. I don’t understand. Can you help me.

There could be a number of reasons for this. Check out all these things here first and let us know the results.’t_showing_up_in_Roon

Thank you for your comprehenisve reply. Unfortunately not sure that it solves the issue. I have taken a few screeen shots which attempt to explain the issue. Under settings/storage you will see that only 699 tracks have been imported from Vault 2 out of a total of

I found the answer. I removed the storage connection to my vault and reinstalled. It now seems to be importing all the files. Unclear why forced scan did not work.