The sync tool isn't able to access the Sage 100 installation location. 


Open the sync tool and on the Integration tab, review the Installation directory field set in the tool:

It's possible someone may have entered a character into this field in error. Try accessing the location which is in the field by going to drive location and the sub folders mentioned. 

It's also possible that someone has made a change the file structure where the Sage company files are located.

To change the location where the tool is pointing to, hit the  Browse button:

Navigate to the company folder location:

Press OK,

Finally Save and Sync:

You should now see your sync's are successfully going through.