Dear Driscoll,
Greetings! Thank you for posting in the Microsoft forum.
When selecting the range of cells, may I know if it doesn't highlight the cell(s) like this (screenshot below)?
From your post, it looks like a display issue, this first thing I will suggest you check Excel in safe mode. Please try opening Excel in safe mode and check if the same behavior appears. To know how to run Office apps in safe mode, see Open Office apps in safe mode on a Windows PC
Also, please click File>Options>Advanced in Excel, scroll to the Display section and check the box beside Disable hardware graphics acceleration. If it is already checked, un-check it and verify if this makes any difference.
In case the issue remains, please provide us with the following information for further troubleshooting.
- Please provide the screenshot of Microsoft 365 Product Information. To get this screenshot, open Word or Excel on the affected device, click File>Account, capture the screenshot of all the information mentioned under Product Information.
- May I know if you have any custom add-ins installed in Excel? Click File > Options > Add-Ins. At the bottom of the dialog box, change the Manage dropdown to COM add-ins, and select Go. Clear the checkbox for any enabled COM add-ins. select OK.
- Does this happen to all the workbooks? Please start a new workbook and check if you experience the same problem.
- If your experience is different than what is shown in the first screenshot, please provide us with the screenshot showing the exact behavior you have encountered.
Let me know the status, I will be happy to assist further. We will look forward to your reply. Stay safe and stay healthy.
Sincerely,
Neha Singh | Microsoft Community Moderator