is there something i can do?

I have my personal movies on an external hard drive. I have linked that drive to a plex server. works great so far. I have recently added HD movies. I cannot get them to play. they start, then stop and a message is displayed you do not have fast enough internet speed to play movie on server. I know I have fast enough service. I have Comcast. 75 mbps and I’m hard wired. I play the media through my apple tv. I know for a fact is has something to do with plex. I also have an xbox one with windows 10. I have cast the same file directly from my drive to my xbox one system and it plays just fine. the minute I use plex through the apple tv, I get the pausing with speed message.

so…

is there something I need/can do to play HD media through my apple tv/plex app?

Without knowing your hardware setup, I can only guess what’s happening - it sounds like your ATV can’t direct play your HD movies so it requests a transcode, and your server might not be able to handle the transcoding in realtime. What hardware runs your Plex Server?

Please provide server logs for more assistance. Close your Plex Server software, wait one minute, start the Plex Server, wait two minutes, attempt playback of a movie that causes the issue, wait one minute after the problem happens, then download your server logs and post them here, along with the name of the file you tried to play.

https://support.plex.tv/hc/en-us/articles/200250417-Plex-Media-Server-Log-Files

hardware should be more that accommodating. amd phenom 2 processor 3.31 ghz. 16 gb ram. windows 10.

You need to provide server logs.

I’m new to plex. but Ill try to gather them

Just follow the instructions in the link I provided and you’ll have no issues gathering them.