https://www.dropbox.com/chooser?origin=https%3A%2F%2Fqa-app.fastspring.com
https://www.dropbox.com/chooser?origin=https%3A%2F%2Fqa4-app.fastspring.com
Only Partial url but the rest of the url is exactly the same.
The only difference is QA4 vs QA. Only QA is working and that hasn't been added to my Chooser/Saver domains.
I have added QA4 to my Chooser/Saver domains.
Can you check you're updating the configuration for the correct app, that is, for the app with the app key you're using in your code for the Chooser/Saver?
If you'd like us to check on this specifically for you, please share the full URL(s) that aren't working as expected. Feel free to open an API ticket if you'd prefer to share privately.