If you can't send your CTS registration to the server, check the following:

Look for any animals with an ORANGE surround in the animal list: 

This means 'Missing Data'. Press the (i) button to get the details:

The missing information will be highlighted in orange!

Fix the issue and try again. All animals with an orange surround will need to be fixed!

A YELLOW surround, means all data complete, awaiting upload to CTS!