Hi Mitchspear,
Please try changing the font, then save the settings, re-start Excel and then change the font again back to normal, check if this fixes the issue. For this, in Excel, clickFile > Options, theExcel Options dialog box opens, then click General from the left pane, if you see the correct font, then select some other font from the default font drop down list, see screenshot:

Then clickOK button to close this dialog, and a prompt box is popped out to remind you to restart the Excel file for taking changes effect. Once you re-start Excel, type in a cell and check if the font type changes or
not, now follow the same process to change the font back to the one you wanted. After re-starting Excel, see if it is fine now. If it still didn’t change, then re-start your computer.
If the issue persists, please provide us with the following information:
- Please provide the screenshot of Office 365
Product Information. To get this screenshot, open any Office app such as Excel or Word on your computer, click File>Account, capture the screenshot of all the information mentioned under Product Information.
- Since when did you start getting the issue, is it after Office update?
- Do you see the same behavior when you create a new Excel workbook?
Thanks,
Neha