Depends on the specs of the video you're trying to edit. (Viewing in a player is not the same as processing in an editor.)
Open one of the video clips you're trying to edit in Media Info or G Spot and note the resolution, frame rate and, above all, the audio and video codecs that are listed.
If the video came from a camcorder, let us know what model of camcorder and what settings the video shot at (resolution, frame rate, format, etc.).
What computer operating system for your Premiere Elements 14 tryout.
What are the properties of this imported video - compressions, file extension, etc.
Download and install the free codec utility named GSpot and tell us what the readings are for Video Name, Codec, Status and Audio Codec/Name Status.
Do you have the latest version of QuickTime installed on your computer with Premiere Elements 14?
Are you running the programs as administrator (from user account with administrative privileges)?
Is your video card/graphics card driver version up to date according to the web site of the manufacturer of the card?
Let us start here, and then decide what next. The tryout is a full feature version.