Hey, @chrisord12!
Have you tried creating an automation from scratch?
I can't say it works this way with Manychat, but there are tools that update from time to time (also Manychat) and may change some code and stuff that doesn't work anymore with new automations.
If this also is true for Manychat, it could be the source of your issue. Duplicating very old automation may duplicate stuff that doesn't work anymore or is incompatible with current features.
I also recommend checking your permissions and general channel connection: Instagram automation troubleshooting – Manychat Help
Hope this helps!
Hi Fabio, thanks for your reply. I tried creating a brand new automation with the same instructions and it was exactly the same. It wouldn't even work in the test mode
I’ve just went through and refreshed all permissions following the video in the troubleshooting page and that hasn't worked either
That's a bummer… 
Your automation seems to be ok… Comment trigger + message marked as comment reply 
The best move may be getting in contact with Manychat's Support Team: How to get support from Manychat – Manychat Help
They will be able to investigate it further.
There's also an extra test you could do, but it will make you lose all your Manychat Contacts that came from this Instagram channel.
If deleting all your contacts isn't a problem, try this:
- Go to Settings/ Instagram
- Roll to the very bottom of the page
- And "Remove Instagram Account from Manychat”
Wait 5/10 minutes until your contacts are being excluded and reconnect your IG account again to Manychat.
This is like a "hard reset” … 
Also, recommended way to connect your account is via Meta Business Suite, instead of just your IG Login. This offers a deeper integration with Meta services and tends to give less integration issues.