The user is not able to access the list which has unique permissions

Question

The user is not able to access a list which has unique permission than the parent, In that case what should be done?

Answer 1

Edit the list permissions and add the user to the list manually, or add the user to a group that already has access to the list.

Answer 2

What is the error message when the user access to the list?

Remove user's permission on the list and re-grant permission for the user, compare the results.

If the issue still exists, try to grant user with contribute or full control permission on the list, compare the results.