Error message: Converting from text/HTML to multipart/mixed is not supported.

This error comes when you have a CSV entered into the Fetch Devices by ID that does not include a Carriage Return (characterCode 13) but instead has a Line Feed (characterCode 10).

The easiest way to identify where this happens is to copy/paste the values from the list of Serial Numbers/Asset IDs window and pasting it into a Google Sheet.  You will see at least one of the rows that have spanned over two cells like the highlighted cell seen below:

Notice that there is no cell divider between the two lines.

Breaking the joined cell into two separate cells will result in a successful pull of the data from Google for the specified devices.