Dear Dorian L.
Welcome to Microsoft Community.
We understand that the Copilot icon is not displayed in your program.
According to your statement, you were able to use Copilot normally before, but suddenly it cannot be used in Microsoft 365 Personal. We have checked and confirmed that we need to explain to you:
Currently, the Copilot function can be displayed and used in applications such as Word, Excel, PowerPoint, and Outlook in Microsoft 365 Personal subscription.
Copilot is now in Microsoft 365 Personal and Family - Microsoft Support
You said that the Copilot icon suddenly cannot be displayed. We are also worried that this may be due to the deviation between the program detection and the system's detection of the license. You can try the following operations:
Update and repair the Office program:
You can open any Microsoft 365 application, go to File > Account, and select Update License. Re-detect and update your Microsoft 365 Personal license information to confirm.
At the same time, you can also try to update the Office program to version 2501 or higher to confirm whether Copilot can be displayed. This can also help the system re-detect your license information and then confirm whether Copilot can be displayed and used.
Go to the "Control Panel" > "Programs and Features" menu to find the Office application, right-click the application, click "Change" > "Yes" > "Online Repair" > "Repair" button, and the Office product will automatically repair in the online state. After the repair is successful, please restart your computer and test again.
You can refer to the detailed information in the following link to help you repair your Office program:
Repair an Office application - Microsoft Support
Confirm that privacy settings are turned on:
Open a Microsoft 365 application (such as Word, Excel, PowerPoint, or Outlook). Select File > Account.
Under Account Privacy, select Manage Settings and confirm that Turn on optional connected experiences is checked
Restart the Microsoft 365 application
Confirm that Copilot is enabled:
You can do this by going to File > Options in Word, then in the Word Options window > Copilot, then check Enable Copilot. Make sure Copilot is enabled to confirm.
You can try to refer to the following links for further confirmation:
How to find and enable missing Copilot button in Microsoft 365 apps - Microsoft Support
Please understand that our initial response may not always resolve your issue immediately. However, we will also respond based on your subsequent help and more detailed information so that we can find a solution together.
Best Regards,
Zenobia.Z | Microsoft Community Support Specialist