Automator problem with Microsoft Office 365 Word

If you are using a compiled version of your Automator action, then you need to load the original editable version of the action and recompile it to an application using the new version of Automator. If you are using any AppleScript or other code within your app, then you may need re-write it for Catalina compatibility. Keep in mind that in Catalina you can no longer create apps or embed code in apps that are 32-bit.

If you previously hard-coded the filesystem location of a particular Word document in an Automator action, you need to review the accuracy of that file and its location now.

If you wrote any AppleScript based on an earlier Word 2008 or Word 2011 Scripting Dictionary, that dictionary and its syntax may have changed support for the new Word in Office 365. You can review that by opening the Script Editor and from its File menu, select Open Dictionary… and select the Office 365 Word.

Microsoft may have changed the name, functionality, or even removed certain Automator actions that were included with older versions of Word.

What Kappy has said.

You have answered my initial questions, including the "hard-coded" question. Is it a Word action that opens the given Word document, and performs a find/replace on it, or another Automator action?

Since I don't have Office 365 installed, I also cannot see what actions Word installs, nor can I debug your two-action workflow here to see what is happening.