I'll give you everything possible for fixing Phone App in Windows 11. Even if you've tried a step please try it over in sequence here:
1) See if you can System Restore to a point before the problem started: https://translate.google.com/translate?sl=auto&tl=fr&u=https://itechhacks.com/system-restore-windows-11/
System Restore is your first line of defense and can take you back to a point before a problem began like a time machine. If it doesn't help then you can undo it. Read about it first in the tutorial above and then try restoring to just before this started. If System Restore is not enabled on C drive do that now so it's available in the future.
If the problem repeats or System Restore doesn't work then check which Windows Updates were installed at Settings > Update & Security > Windows Updates > Update History, uninstall them there or System Restore again, then immediately check for and block the Updates with the Hide Updates tool explained here: https://www.droidwin.com/how-to-stop-only-a-specific-update-from-installing-in-windows-11/
2) If those don't work then try the latest fixes working for Phone app:
Troubleshoot Phone Link app problems & issues on Windows 11/10
(Avoid ad links which intrude into editorial copy, especially DO NOT INSTALL Restoro, PC Repair Tool and Reimage ads)
https://www.makeuseof.com/how-to-fix-phone-link-app-not-working-windows-11/
https://appuals.com/your-phone-app-not-working-windows-11/ (Avoid ad links which intrude into editorial copy, especially DO NOT INSTALL Restoro, PC Repair Tool and Reimage ads)
Phone Link App Not Working or Fails to Open on Windows 11
https://itechhacks.com/your-phone-app-not-working-windows-11/
Top 7 Ways to Fix Phone Link App Not Working on Windows 11 - Guiding Tech
Cannot Receive Or Make Calls Using Phone Link App In Windows 11/10 FIXED - YouTube
https://www.youtube.com/watch?v=jjO_tTqcnBg
3) Try resetting the App using all four options here: https://www.elevenforum.com/t/reset-uwp-app-to-default-in-windows-11.1174/
4) Reinstall the phone app following this guide, then reinstall from the Store app > My Library: https://www.howtoedge.com/uninstall-your-phone-app/
5) If none of these work and you have other performance problems go over Windows 11 with this Performance Checklist to try to find and fix problems: https://answers.microsoft.com/en-us/windows/forum/windows_11-performance/windows-11-performance-and-install-inegrity/4f020fd1-f08c-45a3-8a30-c112f1a0b29f
If nothing here helps then you may be able to help Microsoft improve this product/experience by using the Feedback Hub in Start menu, especially if you are comfortable with sharing relevant data and screen recordings. Microsoft developers DO read feedback from customers that comes in via the Feedback Hub, so that is a great way to share your thoughts on how to better serve you as a customer.
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