If you click on a link to which you don’t have access to or do not have the right to view, this error is displayed.
For example: If you click on a ticket URL, which you don’t have access to,(you could be part of the conversation by being in cc) then you get this message.
The same happens when an agent clicks on the ticket and it would say that either the ticket is deleted or the agent does not have permission to view the ticket.
If you are getting this error as an Agent, please check if you have the correct Ticket Scope (Global access) to view the page.
Please feel free in writing to firstname.lastname@example.org in cases where the error appears in scenarios that are not mentioned above.