I take it that you are doing an online application for UK passport ??/
I had the same issues went to photo shop at Meechok Plaza showed guy photo requirements sizes etc ,photos taken with Canon SLR,Went into scanned and uploaded Rejected .went into CM town centre photo taken with Nikon SLR uploaded also rejected
Got someone to take my photo outside in partial shade on my mobile phone uploaded
IT was Accepted
so get someone to take ur photo on mobile worked for me