User role permissions setting same as group, but different behaviour

I have a list that has Advanced settings or Item-Level Permissions Read access: Read items that were created by the user and Create and Edit access: Create and edit all items.

I have set up a new Role with options ticked as follows:

List Permissions: Manage Lists, Override List Behaviors, Add Items, Edit Items, View Items , 

Site Permissions: View Pages, Open  

I created a new group and gave it this role. 

When I add a user to this group they can see all items in the list (This is what I want. Not all users should see the list as it contains confidential info).

I created a flow and set up Grant access to an item or a folder and set the Role as the new role I created. This works. I can see that the user has been given this role in relation to the appropriate list item when I check the permissions.

However, they can't access the item at all. I can't work out why the role behaves differently for a group than it does for an individual user.