If the wall that it’s painted on is the external wall of a single family private residential property, then it was correctly rejected for being on private residential property as per this clarification:
Note the text about being on the outer facade or outward facing side of a property boundary.
If the building is not a single family private residence, and you have proof of this, you could submit this proof with your appeal when the appeal button becomes available for you (I’m assuming you’ve used both of your available appeals recently and that you’re waiting for the 15 day cool down before you’re given another one to use).