Are you referring to the text service provided by the BBC using the red button on your remote control.
A few years ago. the BBC announced that it was going to stop the red button text service due to pressure from the govt for the BBC to make cuts across its services. Television manufacturers took this on board and decided. not to include the necessary hardware/ software to decode the signal for the text service. Any TVs manufactured after late 2019 or early 2020 now cannot offer the red button text service.
In early 2020 due to public demand and the escalation of the pandemic the BBC decided to back track on their decision and kept the text service going as a public service, sadly TV manufacturers have failed to do so.
Pressing the red button while watching BBC channels should start the iPlayer, or for some broadcast especially sports may give you alternative commentary, and I noticed Glastonbury the red button gave you alternative stages/ artists to watch.
