Movie Studio Platinum 16 was released a couple of years ago, so have the transitions worked for you in the past but no longer do so? If this is the case, what has changed on your computer recently? Do you have the latest build of MSP16 - and which build is that? Go to My Products on your MAGIX My Account and download / install the last MSP16 build if you are unsure.
If you are referring to 3rd party transitions packages, which one/s and have you actually purchased them?