Just writing to report that using the dynamic meta box tags in elementor do not always work. Sometimes do. The occasions I have found it not to work have been:
* Using the dynamic conditions plugin (where meta box is an option) it will not work on many fields but not fields like radio. Although works with some fields!!
* Using the native dynamic colour option in elementor where it should populate with the meta box colour picker value.
A workaround is to use the Post Custom Field and the Custom Key. This works fine and so it is no longer an issue for me. But just letting you (and anyone facing same issue) know about this.