In many cases SkyRoof does not decode telemetry because it does not know the exact signal parameters, such as baud rate and framing. These parameters come from the SatNOGS database and are mostly correct, but for some satellites the data are missing or wrong. You can click on the gear icon and enter correct data - and SkyRoof will start decoding.
There are still some satellites that use framing not yet supported by SkyRoof, for those satellites you can use 3-rd party decoders such as UZ7HO soundmodem, Direwolf, or SatDump - use a VAC to feed the audio from SkyRoof to those decoders. See the How To section in
User's Guide for examples of such configuration.