Can I access data from forms that failed to send-"Error: Generic Exception: Error: (404)

Welcome to the community, @clement.bisai! This post discussed previously should help explain why you cannot send a finalized form to a deleted project.

You could, however, retrieve these submissions as an XLS dataset as outlined in the post discussed previously:

If needed, this support article Transferring forms and data manually from one android device to another should also be helpful to identify the project path from your device.