Transparency shows in program but not when published

I added a shape (canister) over some other shapes. I wanted to make the outer canister slightly transparent so you could see the other shapes inside the can. Within the storyline program, it shows as slightly transparent but when previewed and published, the canister is solid without any transparency showing. Any ideas?

Using a Mac (Big Sur) running apps on windows 10 with parallels.  The attachment is what the canister should look like but instead it is solid.

Nancy