Hi,
unfortunately, it was necessary to update the connection with Xparticles some time ago, and you need Xparticles Build 884 or greater, starting from c4doctane 2020.2.
So, you need to upgrade Xparticles, or you are forced to go back to old c4doctane 2020.1.5-R4:
viewtopic.php?f=85&t=75718ciao,
Beppe