Firefox – tweets centering only works if the page is loaded with a small width

I have added the following styles to to change the size and spacing and horizontally center the feed:

p.rtw_main {
	font-size: 1.2em;
	line-height: 1em;
	margin-bottom: 0;
}

div[id^="rotatingtweets"] {
	margin: 10px 0;
	padding: 15px 0;
	text-align: center;
}

div.rtw_follow.follow-button {
	text-align: center;
}

This works in Chrome and Opera no matter what.

In Firefox, it seems to work as long as the page is loaded in a window that’s narrow enough to cause the text to wrap. If it’s loaded this way, I can resize the screen to a larger width and the feed remains centered.
However, if I load the page with a wider window, the tweets are left-aligned and scrunched to the left if I size the window down.

I don’t have the site hosted yet, so I’m afraid I can’t provide a link, but do you have any ideas what the problem may be and how I can fix it?

https://www.ads-software.com/plugins/rotatingtweets/