A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hello,
That sounds like a rendering issue, but the account change makes me wonder if there is an add-in or setting carryover causing trouble.
Check if this is caused by external interference. Please try opening Excel in Safe Mode. Close Excel completely, then hold down the Ctrl key on your keyboard and double-click the Excel icon to open it. Keep holding Ctrl until a window pops up asking if you want to start in Safe Mode and click Yes.
Once in Safe Mode, create a few borders and see if the disappearing glitch still happens. Let me know the result.