That happened to me a week or so ago. I wish I could remember exactly what I did to get it to go through, but it was rather simple. I believe I just requested any program updates that were available, exited the program, and then rebooted the computer. After that, I just retried transmitting the return.

I remember not really understanding WHY it worked when I retried, but I was happy that it did. Hopefully, I am remembering correctly.

When nothing works, reboot. It is weird how often that fixes things.