Plugins not showing up on Logic Pro x

Hi there!

I recently downloaded the free trial version of a few plugins, and Ive been reading all the articles related, but I havent been able to open them on logic pro x (10.2.1). I keep seeing the error “couldnt be opened”. I tried to uninstall the files and download them again, but nothing happens. Is it maybe because the plugin is not compatible with that logic pro version? What should I do? I would really like to purchase them. I would really appreciate it, if you could shed some light!