Just a query. Is the residential gateway/ modem provided by Spectrum?
If so is PC connected directly to that provided modem or passed through either a switch or isp extender device or perhaps a wall jack rj45 ethernet port using inside wire in the walls.
Also if straight to router is there a port out of usually 4 or 5 grouped ports that are not of the same color or may even labeled as "1Gbps" some go higher when dealing with fastest speeds. Att and Comcast have equipment that use this
Internet speed on PC is largely hardware specific. gpu, cpu, memory, Network interface
As a former tech for the Death Star I would bet its the top suggestions. Lasty the PC...but it is more common than you think of coming up shy.
spenceteeth's post in Speeds on my PC are capped or limited to 820mbps was marked as the answer