Perch API from a subdirectory rather than root domain

Hi, I'm able to access the API data when using Perch on a subdomain (e.g api.mywebsite.co.uk) but not when it's in a subdirectory e.g (mywebsite.co.uk/folder).

I can use Perch fine (in terms of logging in etc) in the subdirectory by changing the site path and login path in the configs, but the API doesn't work when visiting mywebsite.co.uk/folder/api/about for example.

Is there a config setting where I can tell the API to look in the subdirectory and not at root level?

Thanks.