McSarp wrote: "all my photos on my MacBook has disappeared.
My guess is that you accidentally created a new empty Photos Library. If that's the case, you need to find the original one and double click it. The Photos Libraries are usually kept in the Pictures folder.
If you close Photos, and then option-click the Photos icon, you get a Library-picker window that lists all the Libraries that Photos knows about, like this:

As you see, I have several Libraries. One is designated the System Library, and that's the one that Safari and Messages and others can use to get and save pictures, and it's the only one that can connect to iCloud. The System Library is probably the Library that has all your images. The path to a selected Library is shown below the frame. You can choose the one you want, and it will open in the Photos app.
If you don't want this extra Library that you've created, you can delete it.
Is this what's going on?