Thanks for posting in the community! Just to make sure we're on the same page about intended functionality with layers, please take a moment to review our Create Multi-Layered Diagrams article from our Help Center.
You can think of your page as the "base" layer that all other layers are built on top of. When you click on Page, you will see shapes in all layers that aren't hidden. In my example below, blue shapes are on the "base" Page and yellow and pink shapes are each in separate layers. When I select Page, I see all of these shapes together.
If I click into a specific layer, those shapes are active and I can edit them individually, while shapes in other layers and on the "base" Page are grayed out.
If you're not seeing shapes in one of your layers when you click on Page, please check in the Layers panel on the right side of the canvas to see if the "Hide" eyeball shape is checked next to that layer.
Please feel free to let me know if you have any further questions-hope this helps!