Fix an error in MS Access, and link Access database to Excel

I used someone to fix an error in my Microsoft Access database, but the error came back as soon as I clicked on 'sort'. I need this error permanently fixed, as my business database is currently unusable because of it. I also want an explanation as to exactly why this error happened, and how I can prevent it in future. The error message is: You must specify the same number of fields when you set the LinkChildFields and Link MasterFields properties.

Once that's done, I'd like the financial data to be dynamically linked to an Excel Pivottable/Pivotchart. I want to see a bar chart showing monthly income and expenses, combined with a line chart showing profit. The chart should automatically be updated as data is updated in Access.