The hitch with switching into forbearance is that all your accumulated interest will capitalize. This is a bad thing to be avoided.
Rads321, I had the same thing happen to me a few years ago. Call your servicer and tell them that you didn't receive notice to resubmit documentation of your income. They glitch on sending out notices all the time and generally know that there was likely a mistake on their end. Tell them that you want your account to remain in IBR until they process your application and that you do not want your interest capitalized. If the first person that you talk to pushes back, hang up and call again. If you're not getting anywhere the first few tries, ask to speak to a supervisor. Make a note of everyone's name and the date/time that you spoke with them and ask them to generate a letter and send it to you agreeing to hold your account in IBR without interest capitalized until your IBR re-application is processed.
I did this and it worked great. No payment due bigger than my paycheck and the interest didn't capitalize.