I have been suffering for 6 months without pop-up alerts for repeating tasks. I initially had them but they went away after a 2Do app update.
First a brief tutorial for the newbie or uninformed. Since iOS 4.0, 2Do provides pop-up and alarm alerts locally right on your device without going through an apple server. This is a more reliable way to get your alerts since it doesn't require a cellar or wifi connection. This is also why when you go to Settings>Notifications nothing is listed for 2Do. This area is for apps that use the apple server to send alerts to you device. 2Do sets it's alerts locally right on your device so it is not listed there. To get my alerts working again I did the following:
Open the 2Do app. Go to Settings>Alerts>Reset Alarms. Select Yes to reset your alarms. My pop-up alerts have worked ever since.
I am not sure if I never noticed the Reset Alarms feature, or if it has been added in the past 6 months to new releases of 2Do. I suspect that the Reset Alarms will probably need to be done after every new 2Do update. This only takes a couple of seconds to do and is not a big deal in my opinion.
I am very happy to resolve this problem. If I could only have one app it would be 2Do. If the developers could only find a way to tie into Google calender.......