I’m sorry to hear that you’re having trouble with the “Reply All” shortcut in Outlook desktop. Here are some possible solutions:
Check the Keyboard Shortcut: Ensure that the keyboard shortcut for “Reply All” is set correctly. You can check this by navigating to File > Options > Customize Ribbon > Keyboard Shortcuts. In the Categories list, select All Commands. In the Commands list, select Reply to All. Ensure that the Current Keys field displays the correct keyboard shortcut.
Disable Teams Keyboard Shortcut: If the “Reply All” shortcut is opening the Teams desktop app, it’s possible that there is a conflict with the Teams keyboard shortcut. You can try disabling the Teams keyboard shortcut by navigating to Settings > General > Keyboard Shortcuts and unchecking the Open Teams option.
Repair Office: If none of the above solutions work, you can try repairing your Office installation. You can do this by navigating to Control Panel > Programs and Features, selecting Microsoft Office 365, and clicking Change. In the Office Setup dialog box, select Quick Repair and click Repair.
I hope this helps!