4701TL,
That seems to be a Telstra branded Roku box. Is your issue for Australia?
For Australia, episodes 1–9 seem listed as available though the iTunes Store at this time. It seems that 2023 episodes aren’t uploaded to the iTunes Store yet. The Apple TV app might show other content providers that have later episodes already in your region, which may require a separate subscription.
9-1-1, Season 6 on iTunes - Apple (AU)
For the US, all episodes 1–14 except S06E13 seem listed as available though the iTunes Store at this time.
9-1-1, Season 6 on iTunes - Apple (US)
For Canada, all episodes 1–14 S06 seem listed as available through the iTunes Store at this time.
9-1-1, Season 6 on iTunes - Apple (CA)
For issues with specific iTunes Store purchases, please contact the iTunes Store staff.