How to upload an XML file to wishlist in bricklink
Bricklink is correct - 3062 does not exist. Your link shows 3062b, which DOES exist (Don't ask me why the base number does not exist though :) ). So if you change your XML to

    &lt;INVENTORY&gt;
        &lt;ITEM&gt;
            &lt;ITEMTYPE&gt;P&lt;/ITEMTYPE&gt;
            &lt;ITEMID&gt;3062b&lt;/ITEMID&gt; 
            &lt;COLOR&gt;23&lt;/COLOR&gt; 
        &lt;/ITEM&gt; 
    &lt;/INVENTORY&gt;


It should load.

I do not know the answer to the second part of your question: 4211425 translates to ITEMID 3460 in color White, and the Catalog knows this, but the wanted list does not :(.