Shows that were ahead of their time or groundbreaking but weren't given enough by their networks or the audiences to succeed in that period's climate.

He & She
Dweebs
Police Squad
Sledge Hammer
It's Your Move
Selfie

It didn't exactly flop but the obvious example is Star Trek.

'Gidget' was on a single season then was cancelled . However, the production company decided that the viewers wanted more but, since they couldn't recreate the show 'as was' but they WERE able to get its star Sally Field back, THAT is how 'The Flying Nun' took off!

The cancellation of “Gidget” after a single season was a real shame. Had it run 3-4 seasons, it would have become a syndication staple like sister shows Bewitched and I Dream of Jeannie, rather than seasonal filler. They tried to revive it a few years later with Karen Valentine (Sally Field was busy on “The Flying Nun”) but it never went beyond a TV movie pilot.