Hi there, I had the same thing happen to me a few weeks ago. I could send sms but wasn't getting replies. I went into setting and turned data off and back on, made sure I had roaming turned on and then restarted my phone. Once my phone registered with the Fido network again, about 20 texts came shooting in. This may help for you.
I don't keep roaming on and no one I know is sending me texts here any more as I have told them it is not functioning. I will go to a Fido store and if they can't solve, I'll cancel and try a different carrier