I had it on an IPad and it kept telling me no upgrade, so I put it on my phone and did the upgrade for 24.95, and was able to add all the engines onto my phone, then tried useing my IPad again and it would only see the 3 engines and would not allow me to do more engines, but my phone allowed me to do all the engines, so not real sure why it is happening
so not sure why it is doing this, hoping I don't have to do the 25 dollar upgrade on each device.