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Does it still happen in Troubleshoot Mode?

The site now works on Firefox desktop but not Android. I have tracked it down to something related to the Amazon App when working alongside Firefox. When I force a login to https://www.amazon.co.uk/parents/ via a private browsing window, it will log in. When it tries to open in a normal window it runs through the app briefly before going back to Firefox. When this happens, it will not load.

When I set Chrome as my default browser on Android, it all works.

I could not see a way of putting Firefox Android into a Safe/Troubleshoot mode.

Anyone with any ideas?

via a private browsing window, it will log in.

Try disabling your extensions, they usually don't run in private tabs unless explicitly allowed.

When it tries to open in a normal window it runs through the app briefly

You can avoid this by going to Settings > Open links in apps > Never.

I don't have any extensions but this worked: You can avoid this by going to Settings > Open links in apps > Never.

Thanks for your help!