This EXACT thing happened to me when I voted in person today in Maricopa county. Ballot didn't go through the first time and a lady working there told me to flip it upside down.
"One Maricopa County voter also told The Gateway Pundit,
When I put my ballot into the machine in Phoenix, the poll worker told me to wait for a green checkmark, but then told me to hit the red ‘return’ button and pull the ballot all the way out. When I asked if that was normal she told me that it’s been happening all day and that I needed to flip the ballot over and insert it upside-down with the blank side up. She said ‘as long as we get the green checkmark, we know it’s been read properly.’ I do not know if my upsde-down ballot was actually counted properly."