The at-risk rules place a limit on the amount you can deduct as losses from activities. Generally, any loss from an activity (such as a rental) subject to the at-risk rules is allowed only to the extent of the total amount you have at risk in the activity at the end of the tax year.
You are considered at-risk in an activity to the extent of cash and the adjusted basis of other property you contributed to the activity and certain amounts borrowed for use in the activity.
If there is a loss, and the checkbox is marked that Some investment is not at risk, then Form 6198 At-Risk Limitations is calculated to determine the deductible loss. If that box is checked, the screen At-Risk Limitation - Ordinary Income (Loss) will be the next screen and there you would enter the amount of the loss (as a negative number). If this is not entered as a negative, (i.e. -100.00) so it appears as a loss, then Form 6198 will not generate.