That’s strange. All the icons are from the same font file, yet some are visible and some are not. Some things appear to work properly. The icons tied directly to a link seem to work, but the ones tied to a <span> element within do not. Something’s not right with span related CSS. Perhaps the wrong font is being applied?
You say you tried to fix the CSS. Maybe you left a lingering error? Or if you have CSS optimization, that process can sometimes mess up CSS hierarchy. Use your browser’s element inspector tool to examine the far right missing icon (the WordPress logo/icon). It’s specifically the ::before pseudo-element of the span element within the anchor link. All #wpadminbar selectors for CSS rules should all be from /wp-includes/css/admin-bar.min.css. The applied content: property value should be “\f120”.
Go up to the span element itself. It’s font: property value should be normal 20px/1 dashicons. Anything altering or overriding these would be incorrect and needs addressing. If you have CSS optimization, try disabling it. You might try obtaining an unmolested copy of admin-bar.min.css from the .zip file of a WP download and replacing the current one. Be sure the download is for your current version of WP. All versions are available here.
After making any sort of CSS change, remember to flush any caches. Cached CSS tends to be very “sticky” if not flushed.
