Cannot edit Elementor widgets – edit tools missing

When we edit with Elementor, the full edit screen loads. The problem occurs when we click the edit (pencil) icon to edit a particular widget. At that point the editing tools sidebar is completely grey. No tools or edit windows appear. We can still make changes in the front-end editing window, but either the changes are not saved, or if they are saved, they do not dispaly properly on the live site. We can still add a section and add a widget, but after it is saved we can no longer edit it.

We have tried a number of things and in each case the problem persists:
– Deactivated all plugins except Elementor.
– Deactivated and reactivated Elementor.
– Deactivated other Elementor-related plugins.
– Switched to Twenty-Seventeen theme. (We use Twenty-Seventeen child).
– Switched browsers (we tried Chrome, Firefox, Edge).
– Flushed the server cache.
– Rolled back to the previous Elementor version (2.0.11 rolled back to 2.0.10 and back again).
– Checked memory requirements.

Any suggestions?

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