Are you using an SD card with RetroPie that’s been taken from your Pi 2?
Wondering whether to use NOOBS to get the latest pi 3 compatible Raspbian, then install RetroPie – but if you’ve already done this, not sure what to try.
May just run overclock tests in the meantime (but not today unfortunately, haven’t even plugged it in yet).
Reply To: Raspberry Pi 3 is being sold now.