Symptoms
POA OpenAPI method is called from a remote server. Remote server has backnet IP address and firewall allows it to access port 8440 on POA core
However, call results in error "Connection was reset".
If the same method is called locally - from POA core - it works.
Cause
IP address of the remote server is not added to "Allowed networks" in POA "Public API Manager" settings.
Resolution
Go to Top > System Director > Public API Manager > Allowed Networks and add the backnet IP address of remote server
NOTE: make sure that server which you are allowing to access API is secured appropriately, otherwise anyone who gets access to this server will be able to execute API requests to POA with administrator privileges, refer to KB #113949 for more details on hardening security.