A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
Nobody can even hazard a responsible guess without knowing the details involved including values involved, their location & the Solver parameters being used. The best approach is to save the file to a cloud such as OneDrive then create a share link & paste it into a reply here:
Share OneDrive files and folders
It's also a good idea to indicate the Version Numbers of both macOS & Office.