Tab not working

The plugin’s css is being overidden by something so you need a modified version.

Follow the instruction in the plugin’s faq to unhook the plugin’s stylesheet & add the tweaked version of the css below to your child theme if you’re using one or include it via a custom css plugin

.responsive-tabs-wrapper .responsive-tabs__heading { display: none; }
.responsive-tabs-wrapper .responsive-tabs__list__item { display: inline; cursor:pointer; }

@media (max-width: 767px) {
	.responsive-tabs-wrapper .responsive-tabs__list { display: none; }
	.responsive-tabs-wrapper .responsive-tabs__heading { display: block; cursor: pointer; }
	.responsive-tabs-wrapper .responsive-tabs__panel--closed-accordion-only { display: none; }
}

@media (min-width: 768px) {
	.responsive-tabs-wrapper .responsive-tabs__panel--closed-accordion-only { display: block; }
}

/* === Basic design === */

.responsive-tabs-wrapper {
	clear: both;
	margin-bottom: 20px;
	zoom: 1;
}
.responsive-tabs-wrapper:before,
.responsive-tabs-wrapper:after {
    content: "";
    display: table;
}
.responsive-tabs-wrapper:after {
    clear: both;
}

.responsive-tabs-wrapper .responsive-tabs__heading:focus,
.responsive-tabs-wrapper .responsive-tabs__list__item:focus {
	outline: 1px solid transparent;
}

.responsive-tabs-wrapper .responsive-tabs__heading--active:focus,
.responsive-tabs-wrapper .responsive-tabs__list__item--active:focus {
	outline: none;
}

.responsive-tabs-wrapper .responsive-tabs .responsive-tabs__list {
	font-size: 18px;
	margin: 20px 0 5px 0;
	padding-bottom:0;
	line-height: 1;
}

.responsive-tabs-wrapper .responsive-tabs__list__item {
	padding: 10px 20px 5px;
	margin: 0 14px 0 0;
	border: 1px solid transparent;
}

.responsive-tabs-wrapper .responsive-tabs__list__item:hover {
	color: #222;
}

.responsive-tabs-wrapper .responsive-tabs__list__item--active,
.responsive-tabs-wrapper .responsive-tabs__list__item--active:hover {
	color: #606060;
	background: #fff;
	border: 1px solid #ddd;
	border-bottom-color: #fff;
	border-top-left-radius: 4px;
	border-top-right-radius: 4px;
}

.responsive-tabs-wrapper .responsive-tabs__panel {
	background: #fff;
	border: 1px solid #ddd;
	margin-bottom: 20px;
	padding: 20px 20px 0;
}

/* --- ACCORDION  --- */

@media (max-width: 767px) {

	.responsive-tabs-wrapper {
		border-top: 1px solid #ddd;
		}

	.responsive-tabs-wrapper .responsive-tabs__heading {
		background: #fff;
		color: #909090;
		padding: 10px 0 10px 20px;
		border: 1px solid #ddd;
		border-top: none;
		font-size: 18px;
		margin: 0;
		position: relative;
	}

	.responsive-tabs-wrapper .responsive-tabs__heading:after {
		content:"";
		display: block;
		position: absolute;
		right: 20px;
		top: 20px;
		width: 0;
		height: 0;
		border-left: 6px solid transparent;
		border-right: 6px solid transparent;
		border-top: 6px solid #444;
	}

	.responsive-tabs-wrapper .responsive-tabs__heading:hover {
		color: #606060;
	}

	.responsive-tabs-wrapper .responsive-tabs__heading--active,
	.responsive-tabs-wrapper .responsive-tabs__heading--active:hover {
		background: #e3e3e3;
		color: #606060;
	}

	.responsive-tabs-wrapper .responsive-tabs__heading--active:after {
		border-bottom: 6px solid #404040;
		border-top: 0;
		top: 18px;
	}

	.responsive-tabs-wrapper .responsive-tabs__panel {
		border-top: none;
		margin: 0;
	}
}

It looks like this is a background image which appears due to the following rule in your theme’s stylesheet:

.post-entry ul li {
	background: url(images/bullet.png) no-repeat 0 7px;
}

so you can add the following rule to the css you added in the previous step to remove the background:

.post-entry .responsive-tabs-wrapper ul li {
	background: url(images/bullet.png) no-repeat 0 7px;
}

Also I just spotted some minor typos in the css I posted earlier which I have now corrected

That’ll be the bottom padding on the tab list item.

So try changing this rule:

.responsive-tabs-wrapper .responsive-tabs__list__item {
	padding: 10px 20px 5px;
}

to:

.responsive-tabs-wrapper .responsive-tabs__list__item {
	padding: 10px 20px 4px;
}