Hi there @joesciacca,
That Update failed: Could not copy file. error is not specifically a MailPoet error, and generally can be caused by something on the server preventing a file from being written when the plugin is being unzipped/copied to the site’s plugins folder. For example, it could be from running out of disk space, or security on the server flagging the file for some reason. I’d recommend checking with your hosting to see why it might be getting blocked trying to copy that file.
Related: If I delete the plugin and reinstall, will I lose all forms and subscriber data?
Just deleting and reinstalling the plugin would not cause your subscribers, forms, newsletters, etc to be deleted or lost. That said, with the infinite number of different plugin/theme/custom code/etc combinations, unexpected behavior does arise, so it’s always best to make sure you have a complete backup of the site/database just in case! To confirm though: generally just deleting and reinstalling the plugin would not cause the MailPoet data to be deleted.
For that reason, rather than running the update, you could also consider just deleting the plugin, then downloading and installing the latest version as well. Installing via FTP would be another option as well: https://kb.mailpoet.com/article/258-re-installing-updating-the-plugin-via-ftp
