Hi,
Long story short: you can ignore this issue.
This is due to an Apple convention: iOS Safari asks for these files no matter what. However, it also considers icons that are declared in your HTML pages, which the plugin does. So in the end, your visitors will get your high resolution touch icon, despite of these troublesome 404 in your logs.
If you really want to get rid of this issue (404 are soooo annoying ?? ):
- Make sure the plugin has access to the WordPress Rewrite API. To check this, simply access https://www.your-site-url.com/apple-touch-icon.png. If you get the icon for iOS, perfect, go on with the second step. Else, you probably have a security plugin that messes with the Rewrite API and you should give up, really. Nothing wrong with this.
- Generate the favicon agin. This time, in the iOS panel, click the Assets tab and check everything. RealFaviconGenerator will create all icons and make them appear as if they were in the root directory of your site (so /apple-touch-icon-120×120-precomposed.png now exists).