[excel] (Power Automate) ISO strict Open XML note (#594)

* Add information about strict workbooks failing in PA

* Fixing case

* Add link to format

* Update docs/testing/power-automate-troubleshooting.md

Co-authored-by: Alison McKay <[email protected]>

---------

Co-authored-by: Alison McKay <[email protected]>

Author: AlexJerabek

docs/testing/power-automate-troubleshooting.md

@@ -1,7 +1,7 @@
 ---
 title: Troubleshoot Office Scripts running in Power Automate
 description: Tips, platform information, and known issues with the integration between Office Scripts and Power Automate.
-ms.date: 12/19/2022
+ms.date: 03/27/2023
 ms.localizationpriority: medium
 ---
 
@@ -85,6 +85,10 @@ There are two reasons that the parameters or returned data of a script are not a
 
 The signature of a script is stored with the **Excel Business (Online)** connector when it is created. Remove the old connector and create a new one to get the latest parameters and return values for the **Run script** action.
 
+## ISO strict Open XML workbooks aren't supported
+
+The **Excel Business (Online)** connector's **Run script** action doesn't support workbooks with the [ISO strict version of the Excel Workbook file format](https://www.loc.gov/preservation/digital/formats/fdd/fdd000401.shtml). Flows with this type of workbook return a "BadGateway" error when trying to run a script. This is due to coauthoring restrictions. Please save workbooks as the standard Excel Workbook format for use with Power Automate.
+
 ## See also
 
 - [Troubleshoot Office Scripts](troubleshooting.md)