If it are third party plugins, install them again, but don't forget after install to delete those that only were only in trial mode and thus can be deleted after the install with a program as Boris or so.
Sounds like you are using the NewBlueFX package that was bundled with Vegas Pro 14. That bundle will only work in Vegas Pro 14 without a watermark. In other versions of Vegas Pro, that plugin will give a watermark. The only solution at this time is to purchase a package that contains that plugin.