DROID RAZR MAXX

Did you check the notification settings? My HTC has a toggle on the side that allows me to set it that way. Sorry if I'm being too simplistic, but...occam's razor kind of thing.

Could be caused from a host of things. research / read here: Google Search




Moderator's Note: Fixed above Google search link. Sometimes the forum software will misinterpret certain combo of letters, which will break the URL and display various smileys inline. In which case, using a shortcut such as bit.ly will correct the issue.

My wife's did the same thing. She now has new Motorola Moto X. Could not be fixed. Happy camping.

Settings,
Sounds
Ringtone
Sounds...vibrate...both

If that doesn't change it
Pull the battery, then try again
It might need to be replaced

Can't pull battery on a razr.

Hold power button and volume down button at same time for 10 seconds or until phone shuts down. It will take a screenshot first, just keep holding. It's a hard reset. Most times when phone gets goofy or whatever, just do this. Usually fixes problem, unless you have a setting wrong. It doesn't erase anything.

Maybe you accidentally turned the volume OFF by holding down the volume button on the right. You will see a little icon at the top of your Home screen, just to the left of the WIFI signal icon showing that it is on vibrate only.

Just put your thumb on the TOP part of the VOLUME BUTTON and hold it down until the bar goes all the way to the right.

Maybe you've already done this, but this is an easy fix if you haven't. Check settings like MrWizard mentioned.

Are you talking about incoming calls only or is the problem occurring with txt msg and email notifications also.
I have Droid MAXX and turned volume down to vibrate only for incoming calls while hunting. Phone still rang when someone sent me a txt, so had to go to "msg" notification setting and turn volume to vibrate only. Then phone still gave ringtone when email came in, so had to go to settings for notification on each email accoount and set to vibrate.
Long story short, after hunting, reset notifications for "calls", "txt msgs", and all "email" accounts back to normal and then had a terrible time getting them to all ring. I would get ringtone on phone call but not txt msg. After rechecking all "notification" settings, had to finally do a "hard Boot" to reset phone and all seems to be normal again.

As a last resort, do a factory data reset. This can be found by several steps in Settings. Caveat -- this will erase ALL data and apps on the phone, and leave it like it came new from the factory. However, it will often fix a serious problem and save the phone.