To deliver an asset with a viewer preset, you must replicate/publish the viewer preset. (All viewer presets must be activated and replicated to obtain the URL or embed code for an asset.) See Publishing Viewer Presets for more information
about the error log posted, something was wrong with the steps taken because something is null - you can check in jcr or else in config:
libs.dam.components.scene7.dynamicmedia.dynamicmedia$jsp Unable to save imageserverurl and videoserverurl java.lang.NullPointerException: Value should not be null (key = assetType)