According to Monzo support, I received a PayPal refund; however, this wasn’t reflected on the balance visible in the app.
I am still waiting on a further response, but this seems like a very serious bug; if the actual balance of the account, differs from that visible to the user within the app.
P.S. The original transaction is with ASOS, but used PayPal to pay.
I’d be interested to hear the resolution for this 
Me too! I’ve exported all transactions to Excel, I definitely haven’t received the funds. In the meantime, I will not be using my Monzo card to pay for things through PayPal. @alexs
Out of interest, when was the refund processed?
By ASOS - 18th May. (E-mail received)
By PayPal - 18th May. (E-mail received, also states that it’ll go to the card used to pay, and not the PayPal balance)
Quite a while ago then, guessing it’s not in your PayPal account balance? Or been there and used up on purchases since then through PayPal?
Edit
Just seen PayPal said it will go back on the card. Sure I’ve had that before and it hasn’t, so worth checking.
I’ve checked my PayPal account several times; the error is definitely with Monzo.
Call me Scottish, but I know when £46 is mising! 
Latest update:
Thanks for sharing this Dale 
it sounds like that’s similar to this issue then -
If you’re interested in finding out more about why Monzo won’t be using their current card processor anymore & their plans, check out this blog post -
Yes, it was due to a glitch with the card processor.
Correct me if I’m wrong, your balance was correct but there was no item in your feed for the refund?
Correct. That’s what I’ve been told by support. Not very reassured though.
The only way to check is to export all data and add it all up. Then your actual balance now should be your refund amount more than the spreadsheet.
Is that right. Scratches head
Paypal refunds on normal bank accounts (Nationwide and BoS anyway) can often taken 2+ business days to appear in my actual account after merchant has provided a Paypal refund.
something like that! 
the original transaction was processed on the 18th May… it’s June now
It seems the problem was with Monzo’s card processor, not providing enough information in order to make a “feed item”; so the funds come to your balance, but there is not information available.
It’s not a satisfactory situation, if for example you’re returning various things from online purchases, (which I do often) there isn’t a way to check that you have received the money, except watching your account balance constantly.
Works fine for me, I use PayPal quite a lot.