What OS are you using?
What exact version of LR? Help About PS LR.
Please be more descriptive and post the exact error message if there was one.
Please post a screen shot of the full library module.
Hi there I have the latest version downloaded today it's Windows 10 it asked me to type in delete pics so I did in order for syncing to begin and now they've gone off all devices please say there is a way to recover
Did you delete the actual catalog file or just a collection.
The catalog file is not accessible, other than it loads into LR, from the LR program. To delete the actual catalog file you would need to use Windows File Explorer, go to the folder that holds the catalog file (usually in your Username folder under the Pictures subfolder) and then hit the Delete key or Right click and select Delete and then OK button to actually delete that file.
Also Sync with what and where. You aren't being very descriptive in what you actually did and how you did it.
It asked you to "type in delete pics"??? That really doesn't sound like anything Lightroom would do, it sounds like a virus or malware.
You need to restore a backup of your catalog file.