Shared family folder not sharing with family members

Despite constant links and checking that all the correct contact details and devices are all up to date, several members are unable to access a shared family folder from my iCloud. I have double checked and tripled checked the invitations and settings and methods of sharing from airdrop to message to having them in the family sharing settings with full permissions but all they can access is a copy of the folder if I share it with them, not the live folder within iCloud. Any advice appreciated.