7mm Express is alive and well. That name was a short-lived advertising gimmick for what, before and after, was called .280 Remington.
One of my favorite "dead" cartridges that should have made it is .22 CCM (.22 Cooper Centerfire Magnum).
Basically a reloadable straight-wall cartridge with a power level between .22 WMR and .22 Hornet. -Something many small game hunters had been wanting since the equivalent black powder cartridges disappeared 75+ years prior.
It probably never would have been a highly popular cartridge, but it should have had a good following.
Alas, it didn't survive because only Cooper chambered it, it was a bad time in the market, and Fiocchi made just three small runs of ammunition. ...And the brass for two of the lots of that ammunition had a metallurgical problem that caused case heads to literally crack, crumble, or shatter -- if not on the first firing, then very soon after.
So, with factory ammunition having problems and the whole concept of a 'reloadable 22 mag' being wiped out by the brass being unsafe, and Cooper not having the capital to get more ammunition produced with good brass, the cartridge drifted into obscurity and obsolescence.