On what computer operating system is your Premiere Elements 12 running? Have you updates 12 to 12.1 using an opened project's Help Menu/Updates.
Video recorded with cell phone typically is recorded with a variable frame rate instead of a constant frame rate. Premiere Elements does not do well in that situation - symptoms range from out of sync audio to not being able to import the video at all.
The usual remedy is to import the video into the free HandBrake to get the H.264.mp4 version with constant frame rate which you can import into the Premiere Elements project with Premiere Elements' Add Media/Files and Folders....
Any questions or need how to for the HandBrake procedure, please do not hesitate to ask.
I am using Windows 7. I ran one of my videos through the HandBrake program with the constant frame rate option selected, and it stays in synch in Premiere Elements.
Thank you so much for your suggestion.
Many thanks for the great news of your success with HandBrake to get a video version that worked in your Premiere Elements version. Great job of follow through to gain that success.
Please do not hesitate to ask if you have questions or need clarification on your Premiere Elements workflows.