If you created “iC7 Custom Content Link” or “CC3 Custom Content Link”,
Kindly refer to: https://kb.reallusion.com/Product/53040/Im-an-iClone-7CC3-user-how-do-I-merge-my-old-content-library-with-the-new-iClone-8CC4-library-after-upgrading

After updating iC v8.4 (CC v4.4) or above, iClone 7 (CC3) content might fail to load.

To solve this, multiple select the affected content packs in the iC7 Smart Gallery or iC8 Smart Content Manager > Uninstall > Reinstall the content packs in the iC7 Smart Gallery or iC8 Smart Content Manager.

The same applies to CC3 and CC4.