failed attempt to add or update a list item due to duplicate values

You can implement a check within your Power Automate flow before adding or updating list items. Here's a high-level approach using Power Automate:

1. Before adding a new item to the SharePoint list, query the list to check if a similar item already exists based on a unique identifier or key field.
2. If a matching item is found, you can choose to update the existing item instead of adding a new one.
3. If no match is found, proceed with adding the new item to the list.

By incorporating this logic into your Power Automate flow, you can handle duplicate values gracefully and ensure the synchronization process runs smoothly without disrupting the uniqueness of the SharePoint list.