With the exception of a few 'Mutual Aid Dispatch' channels carried on the General Government Services Simulcast, Houston PD, as well as Houston FD, have gone to encryption on virtually all of their channels. Since there are no scanners now, nor will be in the future, that can decode encrypted channels, there is no longer a feed option, other than the listed Mutual Aid channels. See this Wiki page for more information:
Houston Police and Fire P25 - The RadioReference Wiki
Also see
this as to why feeds may not be available.