TUSB2036: Device Descriptor Request Failed

I am designing a circuit that should allow me to connect up to 6 RS485 devices to a computer using a single USB connection. The initial IC (U5) enumerates properly as a generic hub device but the other 2 ICs give me the "Device Descriptor Request Failed" error and do not enumerate. When I used the TUSB2036 as a single USB to 3 RS485 devices I had no issues. That device was configured exactly like the U3 and U4 ICs are currently configured with this setup yet they seem to no longer enumerate. What am I overlooking

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