Apologies for the slow reply, I have been away on holiday for Christmas and I thought I would give both of us a break from this.
This issue has now taken on some more urgency, as I have it on a couple of live sites and I have just discovered that there is an issue that I believe is possibly theme related when viewing the sites in Firefox and that is the text fields in Contact Forms cannot be filled in, it is fine in Chrome and Edge.
You can see that problem HERE
Here is the code from the style.css minus my custom css that it contains, from memory it was something that Colorlib supplied previously and I have almost exactly the same thing on the sites I have used Dazzling on.
Theme Name: Big Mango
Theme URI: https://colorlib.com/wp/themes/dazzling
Author URI: https://colorlib.com/
Description: Dazzling is a clean minimal and responsive WordPress theme well suited for travel, health, business, finance, design, art, personal and any other creative websites and blogs. Developed using Bootstrap 3 that makes it mobile and tablets friendly. Theme comes with full-screen slider, social icon integration, author bio, popular posts widget and improved category widget. Sparkling incorporates latest web standards such as HTML5 and CSS3 and is SEO friendly thanks to its clean structure and codebase. It has dozens of Theme Options to change theme layout, colors, fonts, slider settings and much more. Theme is also translation and multilingual ready and is available in Spanish. Sparkling is a free WordPress theme with premium functionality and design.
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Text Domain: dazzling
Domain Path: /languages/
Tags: green, light, white, gray, black, one-column, two-columns, right-sidebar, fluid-layout, responsive-layout, photoblogging, left-sidebar, translation-ready, custom-background, custom-colors, custom-menu, featured-images, full-width-template, post-formats, theme-options, threaded-comments
This theme, like WordPress, is licensed under the GPL.
Dazzling is based on Underscores http://underscores.me/, (C) 2012-2015 Automattic, Inc.
/* Your custom styles should go right after this line */
/* Theme Options (CSS) */
The full version with all of the custom css is also attached (providing that worked and you can download it)
Wishing you a Happy and Prosperous New Year