I created an ArcGIS Dashboard with an embedded survey (Survey123) by following these steps: https://community.esri.com/t5/arcgis-survey123-blog/survey123-tricks-of-the-trade-embedding-a-survey...
I get the following error using Chrome: "Cannot read property 'join' of null" instead of displaying the embedded survey. Using Firefox, it displays an error: "t.match(...) is null".
From the screenshot you shared, it looks like you published this survey using an old version of Survey123. Could you please update Survey123 Connect to the latest version and publish it again?