Since it was first written more than 20 years ago, AE has NEVER been able to play back video. AE doesn't work like a video editing application because it does different things than a video editing application. You use it for special effects, motion graphics and compositing. In After Effects, you preview. You don't play.
AE can also do slow-motion. I wouldn't count on it for super-slow motion; you need a special camera for that.
But I'm surprised that you don't slow the video down in Premiere Pro. It would be a lot easier/
We will need to know a lot more information in order to help you. A screenshot of your full AE interface would be useful as would lots of technical information such as what (exact) version number of AE you're using (should start with 11, 12, or 13), what version of Premiere you're using, what version number of your OS, what format and codec the video clip is, the specs of your computer and much more.
I'm interested in how you're trying to play it back as well. Premiere and AE handle video very, very differently.
How much experience do you have working with AE? If this is your first time using it, you're in for a surprise. AE is a LOT more complicated than it looks and it's much more complicated than Premiere or Photoshop. You really need to get a solid foundation in how it works before you jump into the deep end. As they say, you need to learn to walk before you try to run and you need to learn to crawl before you walk - (pardon the multitude of mixed metaphors). Getting started with After Effects
Dave and Szalam, thank you for your help.
I may not be using the correct verbiage, but basically I'm just trying to get through the first steps of replacing an Premiere clip with AE composition. I am using the latest Premiere update through Creative Cloud (I updated with the newest version only a week ago). AE is also through CC, but probably not updated as recently. I am using a MAC OS X El Capitan, Version 10.11.2.
When in Premiere, I right-clicked and selected "Replace with After Effects Composition". Once in AE, this is what I see. It will not allow me to "preview" the clip that I have imported so that I can begin doing slow-mo with frame-blending.
**I can do slow-mo in Premiere, but I can't do slow-mo and reverse speed, which is what I need for this clip.
To avoid a time-consuming troubleshooting process, I would suggest that, rather than using Dynamic Link, simply CMD+C to copy your clip, go into AE and CMD+V. It should paste that clip with the appropriate edit points into your AE comp. You may need to press [ to get it to sit at the beginning of your comp and you may need to trim your comp length, but you should be ready to rock pretty fast. Then, simply render the shot out of AE into your favorite intermediate codec, and use the resulting file in your Premiere timeline instead (or on top of it in another track if you want to keep the unaltered clip handy for some reason).