I enter the modal id address or assign a style to buttons in Hype, import as OEM to wordpress - unfortunately Hype buttons do not work (also through innerHTML)
You are using Oxygen and have set the data-trigger-selector="#buttton" … as this is a ID your using to trigger the modal there can only be one trigger per page as ID’s must be unique. If you need more then one trigger use a class based trigger.
Also, don’t use HTML Widget to embed HTML… just double click a rectangle or group and use the small pencil.
No it’s a loading and timing issue. The init for Oxygen works on the jQuery(document).ready and Hype is lazy loaded. The way that Oxygen does it, it’s not easily allowing developers to re-run some function to scan the page again for newly added triggers. So, my suggestion would be just add the trigger to some invisible button/link on the page (outside Hype) like Oxygen expects it and trigger that button once Hype is running from within Hype by delegating the click with JS.