@ChenChen4, are you saying that 1) when you click the "x" next to the red error icons, nothing happens? Or are you saying that 2) you went into your web map, deleted and added some layers, and you're expecting the Feature Info widget to detect those changes?
In case you mean #2:
You can set up the Feature Info widget to either work with the layers in a map widget, or custom set up certain layers (for example, if you don't want ALL the layers in your map to be available in the Feature Info widget). It looks like your Feature Info widget is set up as custom layers. If it's set up that way, you do have to be mindful of how Experience Builder treats data sources. For example, when you bring a web map into Experience Builder, it automatically assigns all the layers in that map a data source ID. If you then go into your web map, delete a layer, and then re-add it, Experience Builder doesn't have any way of knowing you just replaced the layer, so it's looking for something that doesn't exist. You can also break the connection with something as simple as grouping/ungrouping layers.
If that's the case, personally, when I need to replace a layer that's currently being used in Experience Builder, I change its data source in the web map I pulled into Experience Builder instead of actually doing anything in Experience Builder. You can do this via ArcGIS Assistant. Assuming the widget configuration is still valid with the new layer (you haven't changed the schema or something), you shouldn't need to reconfigure anything.
