Many app files backed up directly from the store are encrypted and won't work on other devices. Ensure you are downloading "patched" or "unlocked" XAP files from the community archives.
The AMOLED screens and lithium batteries of the Lumia era are failing. Finding stable hardware to test these archives is becoming increasingly difficult. The Legacy of Windows Phone windows phone xap archive
Install a stripped-down version of the Windows Phone 8.1 SDK tools on your PC. Many app files backed up directly from the
Original retail XAP files downloaded straight from Microsoft's old servers are protected by Digital Rights Management (DRM) encrypted keys tied to the original purchaser's Microsoft Account. To make these apps usable for the public, archivers must use decrypted or "cracked" XAPs, which have had their DRM layers stripped out by legacy homebrew tools like Clutch . 3. Silverlight vs. WinRT Runtime Issues Finding stable hardware to test these archives is
Windows Phone allowed unsigned or self-signed XAPs only through (enterprise enrollment). Enterprises could provision a custom root certificate onto the device and deploy XAPs via USB or web server. This mechanism is the primary method used today to install custom or archived apps on unlocked (or developer-unlocked) devices.
You need a PC running the legacy Windows Phone 8.0/8.1 SDK or the Windows 10 Mobile SDK to get the native deployment binaries.