Be advised that many, if not most local systems have dropped back from using 32 downstream channels to using only 31 since the DOCSIS 3.1 / OFDM channel for the gigabit speed tier was implemented. The gigabit speed tier is delivered via that channel rather than the QAM256 channels.
Is there a downstream channel labeled as "OFDM / PLC or as "Other" being shown ?
What do the modem's signal stats look like ? Try getting them here; http://192.168.100.1
Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.
Post the error log entries in their entirety as well.