I have both Corel Painter 2017 and Corel Painter 2019 installed on my computer. As well as Corel Essentials 4 and Essentials 5. I installed a trial version of Painter 2020. After the trial period it deactivated. All my registered Corel Products still worked. Later I installed a demo of Corel Essentials 7. After the trial period Essentials 7 deactivated and ALL my Corel Products were still working fine.
I would contact Corel about this. As your experience seems to be the exception.