Daft easy-if you had takenthe odd 2-3 mins to just read a little further:

there is a long listing on howtodo by yourself-and cheaper too by seewulf, who is currently also on holiday and mis=-using his pass to full extent.

Dear anna fra Sverige, who travelled on an gamla modell papper pass med dotter (but I think they are tilbaka hemmet now), gives all new posters here that link+more info.

For NO/VY etc; CALL (that is how people used fones long ago mostly) EnTur (the general NO agency that handles all things for contracted jernbaner=railways)

I have read most of the advice and want to do it online.  I’m trying avoid having to make a phone call to Entur, as that is very expensive for me - one person has spend 10 euro trying to get through and no answer from them.  So how do we do it ONLINE   

If you want e-tickets for Norway you must call Entur. 

You should be able to make an online reservation for Norway through DSB udland, but then the reservations are delivered by post. I don't know if anyone in the Community har tried this and I don't know which countries DSB send reservations to and what the delivery time is.

https://www.dsb.dk/en/train-ticket-to-europe/

For what date are you trying to make a reservation for?

On entur.no you can see availability. There are no pass holder quota in Norway, so if seats are available, they can be booked.

Entur are quite good. I called them once on a Friday evening around 22:30, only had to wait a few minutes and then could make all my reservations for Norway, including tickets (with Interrail discount) for the Flåm line. Took about 25 minutes in total and cost less than 8€.

Interrail can normally also book Norwegian reservations but they charge a 2€ booking fee per person and train and then a 9€ postage fee because they can only issue Norwegian reservations on paper. In addition, Norwegian reservations are free of charge with a 1st class pass, but only if you book via Entur (by phone or at one of their 5 ticket offices).