Chosen Solution
Callum Nicholson send it back. That is a failed screen. Of course, if you insist to work on it :-) use this guide Nintendo Game Boy Advance SP Screen Replacement - iFixit Repair Guide Replacement screens are available at places like this
That screen is broken. That usually happens when a screen is bent or dropped, so it could have been damaged during the repair (or as amazon calls it, the renewal) or during shipping. Unless you want to fix it yourself and void any sort warranty of that amazon provides, I would just send it back.