Dear BB2019,
Thanks for participating in the Microsoft Community. I'm an Independent Advisor and I'll help you.
Does this issue happen with a specific Workbook or with all? For instance, if you create a new workbook and type some values in 3 cells with change anything in format, Does happen the same?
In this functionality situation, you could try to repair your Office installation with this Microsoft support process:
https://support.office.com/en-us/article/repair...
Do not hesitate to ask if you need more information.
I hope it has been useful to you.
Regards,
Renzo.