I would check these things:
- Check the security role
Make sure the user has Read permission for the correct table and the access level is set to Parent: Child Business Unit. - Check the business unit structure
Make sure the business unit of the record owner is actually a child of the user’s business unit. - Check who owns the record
Check whether the record is owned by a user or a team, and which business unit that owner belongs to. - Check the correct table
Make sure the user has the required Read permission on the table where the record exists. - Check other access settings
Check the user’s other security roles, team membership, record sharing, and make sure they are working in the correct environment.
Example: Suppose Emma is in the Sales business unit, and North Sales is a child business unit. Emma has Parent: Child Business Unit Read access to the Card table. If a Card record is owned by someone in North Sales but Emma still cannot see it, I would check:
Security Role → Access Level → Business Unit Structure → Record Owner


