Files not located

Hi all,

I bought Adobe premiere elements in 2015. I did a recent update and now (not sure if because of the update or something else) a ton of my files aren't able to be located. The video projects I've been working on now have tons of clips that are showing as "media offline" but I haven't moved the files. I am able to locate the files but when I try to open them now i get a "file import failure" error that the type of file is not supported or the required codec is not installed. Any info or advice would be helpful, thanks!