If you're receiving the message "your connection is not private" on your browser, or "error code received" on WordPress, you might need an SSL Certificate.
Currently, Oliver POS does not support sites without an SSL Certificate.
An SSL Certificate is used to encrypt sensitive information sent across the Internet so that only the intended recipient can access it. This security measure is important because the information you send on the Internet is passed from computer to computer to get to the destination server. Because Oliver POS uses an SSL on its servers, those servers will not allow sites without an SSL to access its data.
For your connectivity to work, please install an SSL Security on your site, or check with your hosting provider if they have SSL services for free as part of their hosting package.