I've just filled in the online form and when I put in Ward No 29 it showed an error when I submitted, I could then only submit it by changing the Ward No to 26. As advised elsewhere, I gave both the VDC and District as Kathmandu and (fingers crossed) this was accepted okay
Note: even if you don't have the accurate ward number, it will not matter on the application. They don't check this--it's a formality only. Just submit 2 digit numbers until accepted ;-)Edited: 26 February 2018, 16:45
We had the same frustration. Arrived here Monday. Frankly no point in doing any of this in advance....don’t waste your time! You must still wait to pay your visa fee and wait to go through visa line. Just fill out the paper form at airport. Make sure you have a pen ready!
It's also possible to download the paper application form, print it and complete it in advance for even less hassle.