Hi there,
Sorry to hear about the save for web issue you're facing, could you please let us know the version of Photoshop you're working with?
We're here to help, just need more information.
You may try resetting the preferences of Photoshop and let us know if it helps.
https://helpx.adobe.com/photoshop/using/preferences.html
Note: Make sure that you back up all your custom presets, brushes & actions before restoring Photoshop's preferences. Migrate presets, actions, and settings
Regards,
Sahil