HL7800 USB not detected

I am using HL7800 modem and I cannot detect it on the USB bus. Do I have to activate it to use the USB? I do not have UART connections setup. Is there anyway to make this work with USB bus? I have USB_VBUS connected to 5V and I even tried turning WAKE_UP HIGH to 3.3V. Is there anything I am doing wrong or am I missing something?

Probably you need to enter +KUSBCOMP in UART first to enable the USB port.

So there is no way to activate USB without a UART connection? We do not have UART setup for the modem. Is there any other way to activate USB?

AT command guide says it is disabled by default

Why isn’t this mentioned in the technical specification document properly? We have a fully designed and built up board with HL7800 and we can’t use it now because the USB is not enabled and there is no way to access UART as this is a fully soldered module.