Power Automate: Object must implement IConvertible in SharePoint

Why?

I have seen the error of ❌“Object must implement IConvertible.” ❌ on multiple places in the Power Platform. Like this Power Apps User Forum post: Solved: Server Response: Object must implement IConvertibl… – Power Platform Community (microsoft.com). Recently Power Automate gave me the same “Object must implement Iconvertible“-response:

What?

My Power Automate Flow was failing because of this error when I was using the SharePoint Connector. However looking at the possible root cause, the fix may also be applicable to other data sources / connectors.

How?

So for a Citizen Developer like myself, this error notification does not tell me where to look… 👀

1) This meant for me to start with verifying what the failing action really does (or should do). In my case it was trying to update the file properties of a SharePoint document library file, with the item properties of a SharePoint list item. Therefor I compared the library to the list and saw a few differences in the present columns / column types:

Apparently a SharePoint Site Collection Administrator had changed not only the display name of a column but also the column type… Power Automate can handle a different display name change fine without needing an update, but the internal name AND the column type need to match!

2) So the next step was to find the actual columns in the library that were changed without me having to check every column individually.

TIP: Open the list / library settings page of SharePoint with the Developer Tool of Microsoft Edge (Overview of DevTools – Microsoft Edge Development | Microsoft Docs) and search for your internal column name in the Elements tab to find the column by the display name💡.

After aligning the columns of the library with that of the list… the error notification was gone without a need for a Power Automate Flow update. So this “Object must implement IConvertible“-response seems to be related to the data model definition of the target data source. Make sure that the input matches the output when it comes to columns and column types.

From that moment on, the previously failing update action started succeeding again 💪👍.