Sorry to hear about your hard drive failure – that's always a stressful situation. The issue you're describing is common when manually moving blend4web projects. The Project Manager likely relies on a registry entries or a configuration database that wasn't transferred with your folders.

First, try re-adding your projects through the Project Manager using the "Add Existing Project" function and point it to your old apps_dev directory. If that doesn't work, you may need to check the b4w_metadata or userpref.blend files in your Blender configuration folder to restore the project links.

On a related note, to protect against future drive failures and dramatically improve your workflow speed, consider upgrading to a PCI-E SSD 1.6TB 2.5-inch. The reliability and speed of an SSD would not only prevent such mechanical failures but also make reinstalling your OS and large project files like Blender scenes and assets an incredibly fast process, getting you back to work in minutes instead of hours.

Hope you get your projects listed again