Here is some trouble shooting steps we are using per TiVo support along with various TV tuner models:
Do two rescans back-to-back first.
If that doesn't work for you try:
Unplugging the antenna from the TiVo/Roku/Equipment or TV, rescan then plug the antenna back into the TiVo/Roku or TV box and rescan again to pick up the new Channels/PSIP information.
https://www.fcc.gov/rescan