Logic Pro 9 not compatible with El Capitan OS

I recently upgraded from El Capitan (Logic Studio 9 was working on this OS version) to high sierra and all of a sudden Logic Pro was ‘incompatible’. So I backed all my data up and downloaded El Capitan again from the App Store and reinstalled El Capitan.

After reinstalling Logic Studio 9 (which takes an age!), it is now saying it is incompatible and I must buy the new Logic Studio. Is there a way round this? I am not buying the new Logic Pro, when I already have a product which does the job!!

Thanks