Why does my Droid say I can't open a downloaded file?

[AC Question]

Why does my droid say i can't open a downloaded file

Downloaded a file on a coffee maker from Google. Phone says can't open

 

[B. Diddy]

Re: Why does my droid say i can't open a downloaded file

Welcome to Android Central! Which phone? What format is the file--e.g., PDF, DOCX?