Hi Janwin,
Thank you for posting, I am here to help. Are you getting any error when you try to save you files?
Did you try to restart you MAC and try again if save feature is working?
Please check if your Microsoft 365 on your MAC is license possible that is the reason why save feature is not working.
Let me know how this goes. Looking forward to helping you out. If you need more help please feel free to let me know. If the answer is helpful, please click "Accept Answer".
Best regards,
Jansher