Losing borders in transition from Excel 97 to 2024 Pro Plus

I have a handy appointments calendar (.xls) that has used Excel 97 on a Windows 7 laptop for a long time.  I want to run this on my latest laptop that has Excel 2024 Pro Plus on Windows 11.  When I open this now, many of the cell borders, most of which are involved with conditional formatting, are either present when they should be absent or absent when they should be present.  The calendar is useless as opened.  I have worked to reformat the cells, but it has taken me hours to get from January to April and some aspects are still problematic, albeit acceptable.  The conditional formatting process is very different between the two versions.  Is there some trick to getting newer versions of Excel to properly recognize formatting from older versions?  I created this calendar in Excel 97 very easily many years ago.  I am not sure I could duplicate it, even from scratch, using Excel 2024.