The sale proceeds from the rental property would be income from the sale of rental property.  Be sure to follow the instructions outlined below to enter this sale in TurboTax.  

https://ttlc.intuit.com/replies/3388350

If you fully depreciated the property then there is no cost or adjusted basis to use against the sales price with the exception of the land value.  If you adjusted your original cost of the property for land before depreciating it, that would be allowed to offset the overall gain.

The software suggested that I delete the property as a rental since it was not rented out in 2017.

You must say yes it was rented all year and yes to fair rental value after you check sold on the situations page for sale to get reported properly on your tax return, even if you didn't rent it.  Then follow the interview questions for TurboTax to report the sale.