Johnnie, assuming this was an update of v15 to a later version of v15 and you are using Pro you have the option of selecting your project, clicking on backup, selecting the appropriate backup and selecting redo.

If however you are opening a version of your project created in an earlier version of WX5 (eg V13), you should be importing the project. You do this by opening v13, going to step5 Export, Export Project. This will create the iwzip file for import back into v13 or any later version.

It is extremely good practice to create an iwzip file frequently, this is far more robust than the backup (& if you move to v16 you can name each iwzip independently to create multiple restore points).

Hello Johnnie ,

I see that you use the versione 16. Try following the esach's suggestions to restore a backup of the project.
If you do not have a backup or have difficulty please send me all project files, so I can check if it is possible to recover it. Go to the project folder, which is usually under C:\Users\yourusername\Documents\Incomedia\WebSite X5 - Professional (yourusername refers to your Windows account) and create a zipped file of the whole project folder, then upload it online using this service: https://wetransfer.com/ . Finally, select the link generation and write it here, so I can download the file.
I'm looking forward your reply, thanks.