Voice to tetx not always working.

[cdestuck]

At times when I try to enter a text, reply to a fb message or other typing items, whn I pull up the keyboard, the MIKE icon to the left of the spacebar appears but is light and color and tapping it does nothing. I cannot tap it and get the phone to receive my voice to text commands. Thus, have to type my message. At other times the MIKE will be real dark in color and speach will work. This never happened with my old 4S but does with my new 5. Any ideas why this happens. Thanks.