Portico plugin not working with OJS 3.1.2

Hello,
We are working to integrate Portico plugin in our installed OJS 3.1.2, we have all nessarey details like Host, Username, Password. But when we try to Export Issue or Export Issue to Portico, we receive error

currently unable to handle this request.

HTTP ERROR 500

Please help us, or let us know any fix available or any configuration required.

PHP version: 7.3