A pity. This explains the large gap between Rihannsu novels, too, right?
Actually, the reason there is simpler. Richard Arnold was irked by The Romulan Way
and made no secret of it. Here's some of the history behind that
Essentially, Arnold claimed that The Romulan Way
was an unsold original novel that Duane had in her files that she added a Romulan plot to in order to sell it as a Star Trek
For balance, this is Arnold's response to Duane's version of events vis-a-vis The Romulan Way
It does strike me as odd that she continued to write Star Trek
fiction during Arnold's reign of terror, including Spock's World
which drew heavily on The Romulan Way
. I guess we'll never know the reasons.
IIRC, the reason Challenger died was because no one bought the one standalone book in the Gateways series. And to be brutally honest, branding it as Challenger instead of New Earth wasn't the best idea, especially when the debut novel is in a major crossover event. At least New Earth would've had some brand exposure at the time.
As far as I know, Chainmail
sold no worse than any other book in the Gateways
I'm doubtful that sales are the reason there was no ongoing Challenger