Some examples are not plotting properly

[Alex Fernandez]

Description

Some of the examples are not working as intended in the main branch. See the last plot of https://mapdl.docs.pyansys.com/version/dev/examples/gallery_examples/00-mapdl-examples/contact_elements.html

When running in local, I get this warning additionally:

C:\Users\afernand\Documents\repositories\pymapdl\src\ansys\mapdl\core\mapdl_extended.py:1219: UserWarning: There are no elements to plot.
  warnings.warn("There are no elements to plot.")

I also encountered issues with 3D acoustic analysis plotting in main branch in my local, but the documentation seems fine.