Lost gradients after saving my files in Illustrator
Hello, I use illustrator 24.1.2 and I apply a gradient in a form like this:

& when I save it and open it later, the gradient disappear, and I have only black color:

I don't know why I lost it, I don't know what I have to do (in options maybe?) to keep it in my .ai or .svg file.
Can anyone help me on this?
