After doing an upgrade of WordPress and all plugins on one of our sites, single_image fields stopped displaying images in Elementor templates. I rolled back to Meta Box - Elementor Integrator v2.1.1 and all seems to work again.
Is this a bug with the latest version of the plugin?
There is a new version of the plugin MB Elementor Integrator 2.1.6 that includes the fix for this issue, please download it here https://wordpress.org/plugins/mb-elementor-integrator/
then you can install it on your site to fix the issue. The new version of Meta Box AIO will be released later.