Hello, how are you? If the system is flagging the new name as invalid we can't help you from here on the forums. However our Support team might be able to help. You can reach them here:
If you would like to submit a Support Ticket for help you can do so here:
https://support.ubi.com
You can also reach out to our Facebook and Twitter Support pages here:
https://www.facebook.com/UbisoftSupport/
https://twitter.com/UbisoftSupport