Too early to buy Norway in a Nutshell tickets?

Yes, you are too early.

So this is the Bergen-Myrdal-Flåm-Gudvangen-Voss-Bergen route? Train tickets for the Bergen-Flåm part I think usually go on sale 60 or 90 days before, buy them at www.vy.no . The ticket for the Gudvangen-Voss bus can be bought from the driver and the Voss-Bergen train does not need to be booked in advance.

Thanks for the information. I was planning to use the fjordtours.com website if that makes any difference. We only have one date that we can do it and if it sells out we are out of luck.

You can buy from that website now. I did that about a month or two ago for our trip in August.

I was planning to use the fjordtours.com website if that makes any
difference.

The only difference it makes is that the tickets will be more expensive since you have to pay their booking fee on top of the actual cost of the tickets.

We only have one date that we can do it and if it sells out we are out
of luck.

It doesn't sell out.

Adding to ticketing purchases options, here is the Norway in a Nutshell website. https://www.norwaynutshell.com
As Badger indicates regarding fjordtours, norwaynutshell also acts as an agent so there is a fee on top of the ticket price. The info on buying individual tickets yourself is in Badger's first post.

We did the Bergensbanen Oslo to Bergen train (no stop offs) on a Saturday in July 2023, a year ago. I had purchased the tickets on the vy.no/en website soon after they became available. Our train showed as "sold out" a few days before our departure.

https://www.vy.no/en

The website is easy to use - however, doesn't like US credit cards. You can use PayPal easily.

I purchased ours about a month ago using the website you mentioned.

I compared prices of all segments of the Nutshell route (Oslo to Bergen) to the NorwaysBest package deal before my 2022 trip and found I'd save at least $100 by purchasing my own tickets. (The Naeroyfjord ferry ticket did come from NorwaysBest.com.) Since the time-consuming part of the deal for me was figuring out exactly what I wanted to do (did I want to spend the night along the way, and if so, where) and what time I wanted to take each of the transportation legs, I felt buying the package from NorwaysBest would save me very little time. That proved to be the case; it didn't take long at all to buy the tickets. Now, if you want to break the trip somewhere along the way and are having trouble finding a hotel room (as I did), that's a different situation; in that case you might want to pay for the assistance of the Norways Best people if they have an inventory of rooms.

Thanks so much for all the replies. I would love to hear about any specific stops along the way. Since we are doing the one day round trip from Bergen I don't know how much time there is between getting off one form of transportation and on to the next. I'm fine with it being a day of looking at beautiful scenery, but wouldn't mind a "pause" somewhere along the way, maybe for a short hike or lunch.