When i do a cut-sweep on one side and mirrored that cut-sweep, the original cut-sweep disappeared, why ?

I tried it in SolidWorks, but not like you,
Now you reset the system options: Tools - Options - Reset.

and if still missing as well, email me your file., so I help more in, and my advice if you are using a "cut swept" like in the picture, it is better to use champer, and setting distance distance.

you can provide an image of your point ...?

Here the step by step I did to make a mirror feature but doesn't seem to accept it ! It stole the original feature .loll May be you know why ?
Thanks

Victor
I don't know why but for any reason I just change in the feature tree mirror step and now it's working. Damn it ! :P
I'm going to give you a big thanks for your support cause no one shoot me a message except you . cheer !