[Steven Levesque]

I’ve been struggling with this too and although this post is 4 years old, adding what I managed to resolve this in case other people read this.

In the Layers panel:
1. Select the layer or layer group you want to set to opacity 100%,
2. look at that circle at the right of where you name your layer, click that, hold, and drag left.

Maybe drag right or whichever direction works but this worked for me. See screenshot below: