Explanation
Graphical user interface Description automatically generated

Box 1: Check the number of items in the collection
If the data in your data source exceeds 500 records and a function can't be delegated, Power Apps might not be able to retrieve all of the data, and your app may have wrong results.
Note: Delegation is where the expressiveness of Power Apps formulas meets the need to minimize data moving over the network. In short, Power Apps will delegate the processing of data to the data source, rather than moving the data to the app for processing locally.
Box 2: Use the Advanced Tools/Monitor feature
Monitor is available by default for all canvas apps. Using Monitor, you can trace events as they occur in a canvas app during the authoring experience in Power Apps Studio, or you can use Monitor to debug the published version of a canvas app.
Example: Consider the scenario where an app has been deployed, and the initial version of the app experiences performance degradation. The app also intermittently generates errors with no clear pattern. Loading data in the app succeeds most of the time, but fails sometimes.
When you check Monitor, you see data operations as expected. However, you also see several responses that have HTTP status code 429, indicating that there have been too many requests in a specific timeframe.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/delegation-overview
https://docs.microsoft.com/en-us/powerapps/maker/monitor-canvasapps