Invoice to be send in email

Invoice to be send in email

Hi, I am using Zoho Books and we create an Invoice through an API, whenever we create an invoice, we often get an error: 

This transaction failed to sync with Avalara

So first of all i do not knowwhat is wrong with it, i clicked Sync Now and it asked me about address incomplete. 

1.If this sync fails, why i cannot see this in my response code so the basis of that i can build my update code which can sync this from api call itself. 

because I also want to use the Functionality of emailing the Invoice, and due to the above failure it does not happen, emails does not go. 

It do not let me send the email

can you please let me know what is the best technique to fix this