It sounds obvious. Maybe even a little patronizing. But the first step is to check that the Facebook pixel is installed correctly. If you're not already using it, install the Google Chrome Pixel Helper add-on. It will save you a lot of time and tell you if the Facebook pixel is installed correctly.
Once that's done, and if everything looks correct, it's also worth usa student data checking that the Google Analytics code is installed correctly.
However, even with all of this set up correctly, it's still unlikely to fix the discrepancies. Sorry. We'll explain why shortly. However, it's always good to check things on your side of the fence first

So let's take a quick look at how Facebook and Google manage conversions.