Update Lightroom to the latest version on each machine. Dot releases can be important.
Or ensure you're opening the correct version of Lr on the laptop - eg have you both Lr4 and Lr5 on your laptop and mistakenly tried to open the catalogue in Lr4?
Open LR on both systems, one at a time, and go to the Help menu item and select "About Adobe Photoshop Lightroom" and check the Version number. If they don't match exactly then you need to Update and or Upgrade the older version to match the newer version.
They both have L5 and i updated them at the same time.... i'm at a loss as they should be the same version. hmmm
So you don't want to go through the simple steps to check the version number on each?
Sorry i didn't phrase my answer well... i have checked both and Desktop is 2015 release Camera Raw 9.0, laptop is Version 5.7.1, Camera Raw 8.7.1 but i can't update my laptop. I have went through updates, went into Adobe and update and they are still different.
Ahhhh i think 9.0 needs a 10.9 operating system! my laptop is 10.8.5!
10.8.5 Mt Lion should be fine for LR CC/6. Do you have a Creative Cloud Photographers subscription or did you BUY LR 6 standalone version.
The newest release of LR need a true 64 bit OS which IIRC Mt Lion, 10.8.x, is a True, Real, 64 bit version of OS X. And if it isn't you can Upgrade OS X Mt Lion to Mavericks from free from the Apple Mac App Store. That is IF your system can handle it. Which IIRC any Mac that can run Mt Lion can run Mavericks.
Your desktop is running LR CC/6 and your notebook is running LR 5.x.x. LR CC/6 is not an Update. It is an Upgrade, IE a newer, newest, release of Lightroom. You also need to UpDATE your desktop of LR CC/6 to the CC 2015.1 or 6.1 version which will included ACR 9.1. You should also install the newest version on your notebook.
If you purchased LR CC/6 as a standalone version, you paid $79 for it, go to this site for the 6.1 update.
If you have a CC Photographers subscription then Open the CC desktop app and check for updates.
Install the CC desktop app on your notebook and install the newest release of LR CC on the notebook.