If you are sure that all requests has successful response, you should get those message's ids. You should have configure your webhook. In those webhook you can catch message status updates. For example there are some common statuses (not sure if there are more): sent, delivered, read, failed.
If you have failed status, there will be error code and its title. You can get more information about error on this page.
Reminder: to send templates you must have configured payment and some balance on your account