Im sorry, that I haven't explained the problem clearly, in my first post. Actually, this took lot of time to understand.
I don't know how to share the design file but, I will explain what happened.... .
This how my model looks after adding all the appearance. I applied them face by face.....,it took a lot of time.

1 . My created model, and notice how I applied appearances to different faces.

2. here, I wanted to creat a new body. so, I started a sketch and extrude it.

3. it was by default in cut option but, then I changed it to 'new body'.

4. here, I have changed it to new body and click ok.

5. now is where the problem starts. when I move the large body down a bit, see all those bodies have lost their appearances 😭😭😭.
6. now, no bodies have any appearence on them.
This may seem a bit, not a kind of problem thing. but, for me after applying those looks on my design [It took more than one hour to do appearance], and suddenly by, a small error all those work is gone..... I was literaly taken a back when this happened. "pretty sure it is a bug. 😁
" sorry for lengthy explanation..... . I will attach the image files below"