On LinkedIn, the selection toolbar or insert actions you rely on elsewhere either fail or never show up at all.
Some sites, and LinkedIn is a prominent example, aggressively block browser extensions and injected plugins. On such pages, in-page features like selection toolbars, text expansion, or insert actions can fail or silently not appear. This is a restriction imposed by the site, not a bug in Omni, and sites change their blocking behavior over time, so a page that worked yesterday can break today without anything changing on your side.
Keep the extension updated, since compatibility fixes ship in updates, and check that site access is granted in Settings, Overview. Use the command palette or the side panel, which run outside the page's own scripts, and capture from the toolbar rather than in-page controls. Omni ships dedicated LinkedIn support, including the 1,000 character comment cap and post permalinks, but no adapter can guarantee every page works when the site actively blocks injected code.