If your icons are turning into a rectangle or disapear after installing Buttonizer, this topic will explain all causes and fixes.
Conflicting versions
It could be that your site has 2 different versions of Font Awesome. A theme or another plugin could be injecting their own Font Awesome script into your site.
There are a couple ways to fix this issue.
1. Change Buttonizer's Font Awesome version.
Sometimes another plugin or your theme uses a different Font Awesome version on your site. Fortunately you can easily change the FontAwesome version.
For example: If you have Font Awesome 4.7 on your site, change Buttonizer's Font Awesome version into Font Awesome 4.
2. Disable import icon library.
If you already have Font Awesome 5 on your site, but you're using a different version, then you can disable importing FontAwesome by Buttonizer.
Click on the gear icon of the Buttonizer dashboard. Then go to Settings > Icon Library > Import Icon Library
3. Use a Font Awesome shim.
Last resort: In rare cases you want to use both versions of FontAwesome. A Font Awesome shim will let you use both Font Awesome 4 and Font Awesome 5 at the same time, it will 'redirect' all changed classnames to their new classnames.
Copy and Paste this script into the header of your site:
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.13.0/css/v4-shims.css">
Font weight
Another possibility as to why it's showing up as a rectangle, is that the font weight is being changed by your theme.
Copy and paste this CSS into your WordPress' Additional CSS:
.fa, .fas {
font-weight: 900;
}
