How to get rid of the "do NOT enter sign" after SDK upgrade

[Paul]

After I upgraded to SDK9.0. The old files still left in the project folder. I had this situation last time. What I did was recreated the project. But is there a better way to fix this?

Screen shot attached.

[Paul]

Thanks Aryan, but I wasn't providing correct information. it was after I changed device from xxAA to xxAC. I checked the project folder xxAA and xxAC both exist.