Error while opening file

It's likely that your file, despite being an .mp4, contains something that's preventing AE from opening it.
Will this file open in Premiere? 
Will Media Encoder handle it?

If one of the above can view it, try using that to re-encode. 

If not, try using another encoder (like Handbrake) to re-encode. If this was created on a phone or screen capture app, it may be using weird codecs that AE doesn't like.

I opened After Effects and then I tried to import and mp4 file, but i
cannot... I tried to change the format file but is not work to

Personal info removed by Mod.

Are you import the file or opening the After Effects Project. What is the extension of the file your opening or importing in After Effects?