Obsidian Minecart

so i gave recently got my computer back, i went to install it on the dotPDN host. as it installe dthe .net framework 4.8, i got this message: A certification chain has been processed, but has ended in a root certificate that is not trusted by the reliability provider i am confused to why this has happenedn, i dont know much computation, so i hope you can figure this out, my OS is windows 7 ultimate, i hope you can fix this.