Nine times out of ten a hard refresh fixes it: hold Shift and click your browser's refresh button while you're on the app.
If it's still stuck, an ad-blocker is the usual culprit — they often break embedded Shopify apps. Disable it for your Shopify admin and reload.
Still no luck? Try opening the Shopify admin in a different browser.
If none of that works, contact support and we'll get it in front of the team.