Hi mbrsolution,
thanks for your answer and hint. I checked and found the weakness in the contact form.
The form does not style the submit button completely. This means it does not overwrite
the property “background-image”.
This means that this property has still the value from the theme and is conflicting with the property “bachground-color”. Some themes like “Twenty seventeen” do not set a background image for buttons and they work fine. Other themes like “customizr” do set this value and do not work with your plugin.
The simple solution is not only to say “background-color: lime !important;” but also to
add “background-image: none !important;”. If you want to check you can use the free version of “customizr” with your “plugin”.
With the above fix all themes work without problems with your plugin. Maybe you want to add this fix to the next release of your software or maybe you want to update at
least the documentation and mention that this additional property might be necessary.
For it works fine now and the problem is solved.
Thanks again and kind regards
Thomas