Why is my I-485 case not assigned for processing after submission for several months?

There is nothing unusual with the response. Also, be noted that EB-5 cases are not comparative with any other employment-based visa categories such as EB-1 or EB-2 or even EB-3 and EB-4. For further information relating to priority dates, look at the Visa Bulletin issued on a monthly basis by the State Department for additional information.

You need to look online for the current backlog at the Houston District office. The schedulers await the district office schedule for appointments.

If your priority date is current, there should not be delays in processing. You should have your attorney follow up with USCIS.

There is nothing to be done but wait until you receive an adjustment of status interview notice or the case goes beyond the normal processing time. In the latter case, you can call the USCIS Contact Center at 1-800-375-5283 to ask them to open a service request.

I-485s are taking significantly longer since most EB cases require interviews now, with EB-5 being the notable exception. All you can really do is to compare your I-485 filing date to the inquiry dates on the USCIS case processing times web page.

According to the USCIS I-485 cases are taking between 9 months to 21.5 months. Since your case was filed in October 2019, it really is not past due as they likely doing background checks.