AvPlan will occasionally show NaNs for fuel and time calculations. This is almost certainly because there is some missing information in your aircraft definition.
Please check the following:
Fuel density. If it has has not been set, AvPlan cannot work out the weight change associated with fuel burn.
TAS values. If the cruise TAS has not been set, you will see a bunch of zeros in the TAS/GS columns, and nans elsewhere (time = distance divided by speed... an impossible calculation if the speed is zero)
Your aircraft doesn't have a callsign. AvPlan identifies your aircraft's performance etc by reference to its callsign, so if you forget to give it one, then things wont go well at all.