What exactly does "restricted to versions 1.0.0 by an explicit requirement" mean?

Mattriks May 2, 2019, 10:28pm 2

There’s another example here
with an explanation in this post

Topic		Replies	Views
"ERROR: Unsatisfiable requirements detected for..." how to understand this? New to Julia	1	1402	May 13, 2019
Package manager: what are "explicit requirements"? General Usage pkg	24	3429	April 25, 2019
Confused by "unsatisfiable requirements" New to Julia	10	933	September 15, 2020
Pkg.add error: "Unsatisfiable requirements" How to understand and attack these New to Julia	15	3855	October 13, 2018
ERROR: Unsatisfiable requirements detected for package Unitful New to Julia pkg	15	2238	August 12, 2020