I've had the exact same issue when flying out of Warsaw on a U fare (award). They were adamant that lounge is not included, and the station manager was also of the same view. I've clarified this with Qatar CS which initially was unsure of their own policy but eventually received the following.
Dear Hunter4vr,
We sincerely apologize.
We have clarified with our Privilege Club Department and they confirmed that full award tickets are eligible for lounge access. The same has been relayed to the concerned Airport team, to avoid service lapse in the future.
We sincerely apologize for the inconvenience this may have caused.
We hope you will provide us with the opportunity to restore your confidence.