Hi Alan,
Greater Anglia are right that it should be valid throughout zones 1-9. I suspect that there is something wrong with the coding on the ticket. This may be down to GA or might be a problem for TfL/Cubic. Can you keep pushing this one?
I’ll draw this thread to the attention of my contact at TfL as well.
As a last resort trading standards may be interested if you can show them screenshot of the purchase process and video of it failing at other zone 7-9 stations.
There is no such instruction that TOCs can’t sell travelcards from outside the zones to include zones 7-9. Examples include Shenfield, Cheshunt, Broxbourne and Watford Junction.