405 HTTP Verb method not allowed error when passing POST API call

[SteveFossey]

Hello all, we have an instance of Epicor ERP running on a W2019 VM and we need to send API calls to it. Other things are already using 443 so we're using Nginx proxy manager to forward the calls. In the Swagger interface, everything works fine but when our application attempts to connect, the POST operation is blocked. The response is "405 - HTTP verb used to access this page is not allowed", and "MethodNotAllowed status code from the target server".

I'm a bit self-taught and not certain if this is coming from Nginx or the server, but everything else works including our usual port forwarding that doesn't go through the proxy manager.

Searching online seems to indicate I need to explicitly allow POST operations, and it seems likely that I have to either edit nginx.conf or add to "edit proxy host" but I'm at a loss to find the correct syntax or commands.

Anyone come across this?

Many thanks in advance!