Wondering if this could have anything to do with Sydney Pro (v2.0.26). An Imagely support blog suggested possible theme issues.
Using free Elementor (v3.0.13) and free NextGEN Gallery (v3.3.20), I added a simple gallery by dragging the NG widget into a test page, saved and viewed, but when going back to edit with Elementor, get this:
"Exception thrown - No utilities registered for
Added another test page… same issue.