My guide worked fine for years. Shortly after the new interface, the guide data is completely empty. Also, the channel names and logos are missing. I am having this problem with Fire TV stick second generation. On 2017 third generation Amazon Fire TV pendant, the guide is fine. The pendant has twice as much RAM as my stick.
I know there was an outage for maintenance Sunday&Monday with Schedules direct JSON service.
They get their data from Gracenote. I don't know if the outage was Gracenote or Schedules direct.
I use Schedules direct and lost all data yesterday for a brief time. It was back up within a few hours.
Have you done a refresh to try and force an update?