Problems with activity for relating rows in dataverse

[Svenny]

Hello,

I am attempting to create a flow that will relate rows in a 1N relationship between two entities. The activities in question looks similar to this, example:

However, I get an error message which I am uncertain on how to handle

Code: "0x80040265"

Message: "Value cannot be null.
Parameter name: s"

I have checked the input values and they all appear to be correct. None of my inputs have a null value, and none of the parameters are named "s".

Has anyone experienced similar issues? Where am I making a mistake?

Sincerely

Svenny