Failing to delete firewall rule



I am trying to use the CFv4 API with a fail2ban setup. I have created a testing block on an IP and I am currently trying to delete it. Currently, I have searched multiple threads, most using the old API, and I have read and re-read the official API Docs multiple times. I am hoping someone can assist me with this issue. So according to official API the following is used to delete a firewall entry :
DELETE zones/:zone_id/firewall/access_rules/rules/:identifier

I have managed to find my zone id as I have got it listing all the blocks currently in place.
I have also found the identifier of the block I want to remove.
For some reason when i issue the HTTP DELETE request it returns the following json:
{'result': None, 'success': True, 'errors': None, 'messages': None}

I am at a loss as to why it doesn’t work. According to the API, all it should need is zone ID and firewall entry ID. Both of which I have added. I am also sending the API key and user name across as is standard in all requests.
Any help would be appreciated,