The current Evolve Plus version is 2.6.6
And the Theme4Press core plugin should be Version 1.3.6, Reduxframework Version 184.108.40.206
Please enable your Parent Theme to disable your child theme, if it works, then something you added in your child theme is causing issues.
Please go to Theme Options -> Shortcodes -> Button and check that the settings are properly setup.
Please post the page URL that you had enter the button shortcode.
I need to look at the source code.