Very small positions cannot be sold through the app, because the blockchain fees to process the trade would cost more than the position is worth. The minimum sell in the app is 2 USDC on most networks and 5 USDC on Ethereum, and when network fees are high a sell a little above that can still be too small to route. The app shows you when a position is below the minimum.
This can happen for a few reasons. A small amount may be left behind after selling a token, which is called dust. It can also happen when a token loses most of its value and your remaining holding drops below the threshold.
The app hides holdings worth under 2 dollars, and anything it cannot price, by default. You can show or hide them from your portfolio view using the "Hide dust" toggle in the app. This removes them from your visible positions without deleting them from your wallet. The tokens are still there on chain, just hidden from the display.
If you want to reach a balance that is below the minimum, you can export your private key at https://fomo.family/export-key and import it into a non-custodial wallet you trust, where the in-app minimum does not apply. Never share that key with anyone, never enter it on any website, and never send it to us. This is optional and not necessary for normal use of the app.