Hi,

I think the reason ITN isn't pricing it for you is probably because you aren't following all of the fare rules, each and every one of them.

I don't know of any ITN FAQ, but here's what I found out.

With the EWR-ATL, the valid routing on NW is EWR-DTT/CLE-(bunch of other cities)-MEM/HOU-ATL

This means that you can only connect through DTT (Detroit) or CLE, but not both. Same with MEM/HOU, Memphis or Houston, not both.

Be sure to note that there is a 7 day advance purchase, make sure you are taking that into account. Also be sure you are booking in the right class (K class). And don't forget that if you stay at one airport for more than 4 hours, it's counted as a stopover, which your fare rule does not permit.

With all that said, I was able to price an ITN like this with fare rule K7AVNR:

Feb. 12 NW 335 EWR-DTW Dep 6:10am Arr 8:07am
Feb. 12 NW 253 DTW-MEM Dep 9:10am Arr 10:20am
Feb. 12 NW 820 MEM-ATL Dep 12:55pm Arr 3:08pm

Feb. 17 NW 827 ATL-MEM Dep 7:15am Arr 7:30am
Feb. 17 NW 290 MEM-DTW Dep 8:30am Arr 11:17am
Feb. 17 NW 702 DTW-EWR Dep 11:55am Arr 1:38pm

This priced at $131.50 including all taxes.

You should be able to do the same through IAH (I did it through MEM because it was easier to find K class availability through MEM) and get the same fare (more or less).

Hope that helps.