'Forbidden - 403' error while exporting a Query from Ad Manager? Here's why (and how to fix it)

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.

The cause

Here's the exact scenario that triggers it:

1. Log into Google Ad Manager with one Google account
2. While in Google Ad Manager, swap to another Google account that has access to the same Ad Manager account
3. Export a Query and you will get the Error 403

The fix

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!