When I open my map projects in ArcGIS Pro, the previously joined data is now all <null> in the attribute table

[Srygl1sl]

I know that the join was successful and the data was not null in the past, because I have made and exported maps from this project file.

However, when I opened it today the attribute tables for all of my layers show the joined variables, but they are all populated with <null> as the value. What is causing this and how can I resolve it and prevent it with future projects?

[Srygl1sl]

My workflow (shared with others) requires that the joins be to the file locations in the catalog folder connections- so bringing it in as a feature won't be a sustainable fix.

When I select the excel file in the catalog, it buffers, returns the error below an then I t a red exclamatin point beside it offering to "repair it". Selecting that option doesn't change anything. The error I get is:  "exception of  type 'ArcGIS.Desktop.Core.Geoprocessing.GPItemException"

[MrRamonG]

I know it sounds strange, but in the past, when I was having ArcGIS problems with Excel files, I would open and close Microsoft Access and that would fix the issues. Opening Access would force the computer to install some updated database drivers.