Can somebody please help me? My Mac will not recognize server after I download it

Really need some help! I followed the steps to download the media server, when I went back to the Plex page its acting like I didn’t download anything and is prompting me to download the server again. I can’t get into my preferences because it says there’s no server. But when i click on the server i just downloaded either nothing happens or it takes me back to the page to download. I just paid for an entire year and its appearing now that i cannot use this. I’m not exactly computer literate, any help i could get would be much appreciated