Ever tried to export a Query from Google Ad Manager (formerly DFP - Doubleclick for Publishers) and got a "Forbidden - Error 403" message? This used to happen to me intermittently and it took a while to work out why.
Here's the exact scenario that triggers it:
Fortunately, there are a few solutions and they are all pretty simple. The simplest one is not to swap between Google accounts while using Google Ad Manager.
Alternatively, before exporting a query, swap back to the account you originally logged in with (assuming that account has access to the query you need).
Failing that, log out of Ad Manager completely and log back in with the correct user.
But why would you be swapping between Google accounts in the middle of a Google Ad Manager session? The reason in my case is that we have a master account and then a number of individual users. Some Queries belong to the master account and others to individual users, so it is occasionally necessary to swap accounts in order to acess a specific query. So the real fix is to make sure that all users have access to all the Queries they might need!