Typically this is due to not having the "Deflight-events-module" in your community folder of MSFS. It will automatically be installed when you install the software but for whatever reason it did not, or it was manually removed, we include the module in the application folder.
Go to x:\Program Files\DeFlight\Skalarki SA Driver. You should see a folder marked "deflight-event-module". Copy the entire folder into your community folder of MSFS. If you do not see it or still are unable to locate it. We have attached a copy of it below.
To locate your community folder, take a look at the following site.