Hello,
The error is referencing a second "Apply to Each" loop, though (specifically, one named "Apply to Each 2").
The error does not seem to mention your condition, so I'm going to proceed assuming that the condition is not the immediate issue.
I have a suggestion based on a hunch, and then if that doesn't work, I have a question and a request from you in order to help us further investigate this:
**Make sure that for whichever "list tasks" action (Old Plan or New Plan) you are referencing in the first Loop, you are referencing the OTHER "list tasks" in the second loop. I know that sounds basic, but it could be easily overlooked.**
If that isn't the issue, please address the below:
1. Is there still a loop in your flow called "Apply to Each 2"?
2. can you please provide a screenshot of the rest of your flow?
Respectfully,
Kyle