Repair Corrupted Excel Workbook

My main Excel workbook refuses to load correctly. The moment I try to open it, Excel throws the warning: “Excel cannot open the file because the file format or file extension is not valid.” If I continue,... (Budget: ₹600 - ₹1500 INR, Jobs: Data Recovery, Excel, Excel Macros, Excel VBA, Microsoft 365, Microsoft Access, Visual Basic, Visual Basic for Apps)