There are many causes to this issue but below I will discuss the one I experienced and how I resolved it.
The thing is, few days ago, I'd created a role called 'Store Owner' & assigned to it some permissions. Yesterday, I renamed the role to 'Store Manager' and assumed that like other CMS that I use viz. Drupal, changing the role name wouldn't revoke the erstwhile granted permission to the renamed role biz. 'Store Owner to Store Manager.'
Once I granted permission to the newly created role my problem was resolved.
Hope this helps!