Confluence is not indexing attachment labels.
These are not added to tag clouds, and popular label macros.

Steps to reproduce:

• I am on the Confluence Dashboard. I have system-administrator rights.
• I click "Add space" and create new space (just name, blank space, no restrictions).
• I click "Add page" and create new page (the same as above).
• I click "Insert"-> "Other macros" -> "Attachments", and save page.
• I drag files from my desktop onto the Attachments macro. Attachments are beeing uploaded.
• In the column "labels" I click pencil icon, I type the name of attachment (for example dh or test_label), click "add", click "close". Attachments are shown next to files.
• Then I insert to the page any label cloud macro (popular labels or tagcloud). It doesn't show attachment macros. However when I add labels to the whole page it displays those properly.
• When I click "Browse"->"Labels" there are no attachemnt labels displayed too.
• However when I am on the page with attachment macro, and I click a label next to attached file it, it opens the site https://ourcompany.com/label/clicked_label and it shows all files with clicked_label.