When you reinstall Windows from a clean USB/ISO, it doesn't include some customisations which the Microsoft Store requires in order to let you download and install the "My Dell" app.
The "My Dell" app can be helpful for managing power/thermal profiles and charging customisations as well as some other things, too.
You need to set some values in the Windows registry to make Windows think it's a Dell-installed copy of Windows.
Press Win+R to open the "Run..." prompt. Type "cmd", then press CTRL+SHIFT+Enter to launch it as an administrator.
Paste the following commands into the black window:
REG ADD "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Store" /v OEMID /f /t REG_SZ /d DELL
REG ADD "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Store" /v StoreContentModifier /f /t REG_SZ /d "DELL_XPS"After this, you'll need to reboot your computer.
Finally, you'll need to open the same run dialog again, this time entering "wsreset.exe" and then hit Enter. This will clear the data for the Microsoft Store (it won't affect your existing apps) and ensure you should see the My Dell app in the store when you search for it.
If it still isn't working, and you're using Windows 11, you can try using the Microsoft-provided winget tool included by default.
Press Win+R to open the "Run..." prompt. Type "cmd", then press CTRL+SHIFT+Enter to launch it as an administrator.
Run:
winget install 9PN7T3JFPRZ6
9PN7T3JFPRZ6 is the winget identifier for the My Dell app in the Microsoft Store.
Hit y to agree to the terms and conditions to install the app.