Sorry to hear about this issue mantralbk.

Here's more information about reminders:

https://www.rememberthemilk.com/help/answer/android-reminders-alerts

If you're not having any luck, do contact us via support and we can discuss your issue and get things working again for you with more information.

Let me know how you get on!

What phone and version of Android are you using.
I am having problems with notifications on Samsung Galaxy S8 running Android 7 Nougat.
The notifications are very erratic, sometimes I will get them other times they do not appear.
I have escalated to RTM support who are investigating but no progress to date.
I suggest you email RTM support with as much detail as possible.

Samsung s5 Marshmellow 6.0.1
I'll check the other device but I believe it is s8 android 7

Both never have received notifications through sound/vibrate (pro account)

Tristo, tried everything and all combinations... still not working

Looks like it could just be for reminders that it doesn't work

I also escalated this problem to Samsung and they replied as follows;
"This is to acknowledge that we have received your email. I understand that you're experiencing issues with your Galaxy S8. We apologise for the inconvenience that it may have caused you. In reference to your concern, please consider the following troubleshooting steps to isolate the issue.

Perform a soft reset on your device. This will set your device to factory default but no data will be affected. To reset your device, kindly press and hold the power and volume down buttons for about 10 seconds.

Clear the cache partition on your device.

1. Turn your device off, if it isn't off already.
2. Once the phone is off, hold the volume up, power and the Bixby buttons at the same time for 10 seconds. Keep holding the buttons until you see a Samsung Logo.
3. Using the volume down button, scroll down to wipe cache partition.
4. Press the power button.

Please let us know the results of the troubleshooting steps provided for us to further assist you."

@mantralbk
I did this last night and my two notifications due this morning worked ok. I suspect this is not a permanent fix as turning the phone off/on again also seems to start the notifications working for a time, but worth a try.

As suspected the suggestion from Samsung was not a permanent fix.
Just to make sure I carried out the Soft reset and cleared the cache again but the erratic notifications continue.
I have notified Samsung, waiting their reply.
I am also continuing to feedback information to RTM support on the problem.

I have upgraded the Samsung S8 to Android 8 (Oreo) and Samsung Experience 9 (was TouchWiz) and the notifications are now working ok.