I had a flow pretty much the same as this, and had the same issue. The resolution was more a thing of chance and desperation. What I did:

1. I removed the loop (mine was the "Apply to each" which is the current name for such loop, I believe) and the source of the loop (in my case "List rows present in a table" from Excel).
2. Re added the source (for me the Excel step, for you it'd be the "Get calendar view of events").
3. Saved the flow.
4. Added the "Apply to each" loop (empty).
5. Saved the flow.

After successfully saving at this stage, I could add and edit edit the condition and everything else. Here's the image of an execution and how my flow is (StackOverflow won't let me paste the image here): PowerAutomate Flow

As I mentioned, this only makes sense attributing it to chance, it should have worked from the start but saving after adding each single component worked for me.