The Photo App does not work in Facebook’s default browser. You will be able to edit your photo, but when trying to save and download, you will receive a “Page can’t be loaded” error.
Disable Facebook In-App Browser
By default, Facebook for Android opens the link in the in-app browser.
If you want to open the link in your default browser instead of the in-app browser, then you need to disable Facebook in-app browser and here are the steps: