User who have Read or Contribute permission on the list can not search, they will not get an results

We have a team online sub-site and inside the sub-site we have a custom list. now if a user who have read or contribute permission on the list try to search an item which the user can view or contribute on it the user will always get :-

but if a user with full permission or site admin try to search the list the user will get the related results.. any advice what could be the issue? Thanks