Access to most parts of Fastoche are controlled by staff User Rights. Typically, a user will not see buttons and links to sections they do not have access to. On occasion a link may be visible to direct staff to a page they do not have sufficient rights to view and this message appears. This can also occur if users send direct links to users who have less user rights than them.
If you are trying to determine what user rights are required for a staff to access a certain section there is a tool that provides this information. While logged in with a staff PIN with full rights, navigate to the section, click on the Help icon at the top right and choose User Rights. This will display a popup with the rights that are required to view that page as well as rights that may be required for some actions on the page.