Try to back up your iPod touch first and then make a restore for it. If you have old iTunes backup, just restore the backup to your iPod touch. My iPad had same problem with your iPod touch and I fixed the problem by restore.

Lucky you!

Thank you for your suggestion. But my iMessages...it is another long history. My iMessages doesn't work (my phone number cannot be checked under YOU CAN BE REACHED BY IMESSAGE AT and I have to send & receive iMessages via my iCloud account) for a long time after updating to iOS 11 and I tried...

Thank you for your reply. Tried hard reset, reset Network Settings, also called carrier about my text message service, but they didn't work. Anyway, I will try to update to the 11.0.2 today. Hope it will work.

I just cannot send text messages after updating to iOS 11. But iMessages can be successfully received and sent by my phone number. Trapped by this for more than one month since I updated to iOS 11 beta. For now I used the public version iOS 11 but this issue existed still. Can anyone help?