Why can’t I get my local channels on the Spectrum app?, all other channels seem to work fine.
This is a question best directed to Spectrum. It is their app -- they created it, maintain it, and supplied it to Roku.
Note that at this time Spectrum and Roku are negotiating carriage terms for the Spectrum app and until this is settled the Spectrum app cannot be downloaded to Roku units. So don't delete your current Spectrum app until a settlement is reached.