Not a single astronaut or cosmonaut out of the hundreds who have been in space has stated that the world is not round. They have provided volumes of photographic, video, and eyewitness evidence verifying what we had already known for centuries - we live on an oblate spheroid.
The problem is that a small but noisy group of folks with strong religious tendencies, a poor grasp of scientific and engineering principles, and highly developed distrust of any authority have refused to accept any of this evidence, and are convinced that NASA is hiding the truth. Somehow, in a world of whistleblowers and leaks, these astronauts along with thousands of NASA employees, multiple world leaders, contractors, and scientists have successfully aligned in a sinister global (ha!) conspiracy to pull the round earth wool over our collective eyes for the past six decades. When confronted with evidence that has been corroborated with science, they use ad hominem attacks and other logical fallacies to try and discredit the sources. The Internet and social media (which strangely enough rely on satellites orbiting a round earth), coupled with an epidemic of poor critical thinking skills, have given them a far greater audience than they deserve.
Don't be part of that audience.