A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
This is bug. Hope microsoft will fix it soon.
You may try workaround in this link.
Clicking specific cell doesn't open hyperlink in excel online - Microsoft Community
Found out that if I shrunk the column width less than the link's length, the hover over action worked afterwards. If the column was wider than the link, then the hover over action won't work.