Please download the native program v2.12.5 from GitHub releases in the repository (specifically,
firefoxpwa-2.12.5-x86_64.msi).

Update: If you still have problems after updating to 2.12.5, make sure that the native version mentioned in the extension settings (About the project) is also 2.12.5. If it's not, uninstall the native program from the system settings and try again. You can also try to run "Patch profiles and runtime" from the extension settings.