I am not sure how long this has been happening but I don’t appear to be getting any notifications for transactions even though it is set to on and have previously received these.
I have the android app and it says I’m a beta user if that helps. Version 1.27.1
I haven’t been receiving any either, was asked by support to re-install the app, haven’t got round to doing that yet…
I have the same issue - Just had a chat with COps have said;
I’ve passed this on to our tech specialists who’ll look into that now.
It’s the most useful feature of Monzo and annoying really that it’s not working 
hope they find the issue soon and fix it 
I have Android 8.1 on OnePlus 5 and latest Beta version of Monzo app.
Clearing app data / reinstalling will most likely workfor you 
I had a very similar issue once (at the beginning of the year) and a quick reinstall of Monzo squared away my missing notification sounds, I’m guessing the same should apply to your missing notifications
A reinstall should work, have you tried that? If not, tech specialists will work out a fix for you 
Yes reinstall was the first thing I did before getting in touch.
I’ve seen this happen intermittently on my OnePlus 5
Edit: most recently I didn’t get one for my rent payment going out
I am on OP5 as well and I have tried everything clearing data to uninstall/reinstall but notifications are still not working. 
On chat they told me someone will come back to me yesterday but nothing yet.
I’m having the same problem (for about a week). I did think it was due to having the app open at the same time, but that’s proven to not be the case (had an online transaction this morning - over Wifi - which definitely didn’t trigger notifications - and delayed personal emails meant I wasn’t at all certain the merchant actually took the payment!) [added: a Google Pay payment also failed to flag up a Monzo notification - this time via 3G]
Checked Monzo App->Settings->Notifications->Transactions and payments ARE enabled.
Checked Android Settings->Notifications->Monzo and ‘Block all’, 'Show silently and ‘Override do not disturb’ are all off and ‘On the lock screen - show all notification content’.
Current App 2.0.0 beta branch - last updated 13 hours ago (and I think there was a 3rd version earlier in the week which didn’t have notifications). Android 7.1.1 on Nexus 6.
[Perhaps we could have an ‘Advanced’ setting under Account with things such as ‘Test notifications: See what a notification would show on your phone’ which may help diagnostics]
Monzo COps are just not taking this as a problem on their side. I been advised to wipe my phone off and install everything again. This just doesn’t make sense because every other app is working and I am getting notifications.
At least I wasn’t alone with this issue! I have now uninstalled and re-installed the app and giving it a quick test with success.
Thanks for your suggestions and glad my notifications are back.
Also on a OP5 and have no notifications, Tried reinstalling and nothing happened. The main reason I use it was for that feature, in its current state I may as well go back to my high street bank card since its just as annoying to keep track of
You should speak to the in app chat and see if they can suggest anything
Edit: don’t have this phone but quick google shows lots of people are saying to make sure advanced optimisation under battery optimisation is off and that sorts it for other apps. Have you tried that?
Yep recently saw that after doing more digging, I’ll update if that resolves the issue, it looks like an OS upgrade wiped out battery optimisation settings
I’ve had issues with push notifications on other Android apps previously and turning battery optimisation for those apps fixed it.
Why this happened suddenly is confusing me though.
This is happening (or not happening) for me too with a Oneplus 3.
I loved the notifications when I got my then Mongo card, but lately do not see them. I have tried turning off battery optimisations and also reinstalling the app, but still get no transaction notifications.
The only notification I did get after reinstalling the app had a blue dot to show I had a golden ticket.
App version 2.1.2, Android 8.0.0, OxygenOS 5.0.3.
I have not received card payment notifications for a while now, however, I have got round this with IFTTT.
Shouldn’t have to for a feature that was already available, but it suits my Samsung S7 for now.