When lenders use the term "Rural" it can be very frustrating for a borrower because the term is rarely clearly defined. It can also mean different things to different lenders. Even if the property is centered in a city with a population of 30k it may be considered rural due to other factors. Underwriters will look at the population density of the surrounding area. They will also see how far away it is from a large metropolitan area.
Underwriters want to see that the property is in an area that will support the valuation of the property with numerous comps so they can have confidence in the appraisal. They also want to see that there will be a thriving rental market to support the property and that it is in an area with growth in case you need to sell the property.
Providing a location for your property will help us understand the issue better. Also, how does the property cashflow? How much in reserves do you have? How many properties do you have in your portfolio? Are any of those properties in this area? All of this information would be important for an underwriter when considering a rural property.