I just moved my number to koodo I have received and sent text that have worked but I have also sent some that haven't worked and had some sent to me that did not worked. I has been one number in particular that has not worked. I have been able to call and receive calls from that number
Try doing a battery pull, while the phone is on pull out the Battery & the SIM Card for a minute & then replace them & try it.
If that doesn't work make sure that you are texting the full 10 digit #
If you brought a device from elsewhere to koodo then make sure your APN settings didn't change to a different provider. If there is any other APN listed then delete that other carriers APN.
If neither of those seem to work then call koodo support because then chances are the issue is on their end.