Start the app from the Add-ins tab on the Ribbon or with the command FixRefs. 

This is how JTB FixRefs find the missing reference file:

For example, when your old file path is "T:\A\B\C\D\E\Your Ref Filename", and you move your host drawing to a new folder "M:\New Location\Project 1", and you change the subfolder structure a little, then JTB FixRefs will check these file paths to see if it is available:

"M:\New Location\Project 1\A\B\C\D\E\Your Ref Filename"
"M:\New Location\Project 1\B\C\D\E\Your RefFilename"
"M:\New Location\Project 1\C\D\E\Your Ref Filename"
"M:\New Location\Project 1\D\E\Your Ref Filename"
"M:\New Location\Project 1\E\Your Ref Filename"
"M:\New Location\Project 1\Your Ref Filename"

In case all those file paths do not exist, you must enter the new file paths in the Fixed Paths column. Since it is a spreadsheet, it is easy to do using copy-and-paste tools

You can select the whole spreadsheet, and copy and paste it into Excel. Then, in Excel, you can edit the paths using Excel's more powerful tools like Find and Replace, functions, etc. Finally, paste the data back properly to JTB FixRefs.

There are two tabs in the JTB FixRefs windows: the "Drawings" tab and the "External References" tab.

On each tab, you can see additional info on drawings and reference objects: error when opening drawing, error when saving drawing, drawing version, file not found, the object is unreferenced, and error when running fixing.

The installer that ran when you downloaded this app from Autodesk App Store will start installing the app. Or, double-click the downloaded installer to install the app. You may need to restart the Autodesk product to be able to run the app.

To uninstall this app, exit the Autodesk product if you are currently running it.

On Windows 11 and 10 version 1703 or later press Windows+I on the keyboard to access Settings or click or right-click the Windows Start button and then select Settings. Click on Apps (optionally followed by Apps & features). On older Windows versions click Control Panel > Programs > Programs and Features or Control Panel > Add.

If your drawing is already open, the renamed object won't appear on the External References palettes until drawing is saved and reopened.