Error The following email template started is missing PRESTASHOP

It is likely that you lack the translation of that email. If you have access to the files, go to themes / yourTienda / mails and make sure that in all those subfolders (at least one call must be 'in') there are the same translated files in the language that corresponds to the folder.

UPDATE

I downloaded the module and after analyzing it I located the problem. During the installation of the module the necessary statuses have been created automatically and all have been indicated that they must send emails by default.

However only four of them have templates, which are (in English, I do not know if you will have them translated) Transaction in Process, Transaction Pending, Transaction Chargedback and Transaction Pending.

The rest of the states do not have templates in the module and even then they have been told to send an email when an order changes to that state.

The solution would be to review the states and uncheck the option to send email in the prestashop configuration. In prestashop 1.7 if I'm not mistaken it's in Settings > Store parameters > Order configuration and there is the "States" tab. Find the transaction start status (if it is not translated it would be "Transaction started") and uncheck the option "Send an email to the client when your order changes state."