Excel Online Data Visibility Fix

I depend on a long-standing Excel workbook for daily data entry and finance tracking. Everything behaves as expected in the desktop app, yet the moment I open it in Excel for the web a chunk of the information—entire rows and sometimes whole columns—goes missing... (Budget: $10 - $30 CAD, Jobs: Data Analysis, Data Entry, Data Management, Data Processing, Excel, Excel Macros, Excel VBA, Visual Basic)