I would re-install Excel to start with. I'd also, in Windows Update, select 'Give me updates for other MS products...' and try some manual updates over a couple of days
If this is urgent then use the GetOffice app and get a trial version of Excel 2016
Or, if you want something permanent AND your spreadsheet are not a foot thick in links and Macros download LibreOffice which works fine under W10
Personally I just updated to Office 2016 but that is not free.