The key thing to remember about Polkadot ecosystem tokens
Being a user of the Polkadot ecosystem means that there are lots of different types of token standards that you should be familiar with.
The most common user mistake in the Polkadot ecosystem is sending tokens to an exchange from the incorrect chain. For example, if you send DOT tokens from the Asset Hub parachain to a centralized exchange (CEX), it is very unlikely that you will receive your DOT tokens on the exchange.
This is because the CEX has configured their wallet to only show you DOT tokens which have been received on the Polkadot relay chain. In reality, the CEX has indeed received your DOT tokens, and they will actually be in your account (on the Asset Hub parachain), but it will likely take you a long time to convince the CEX to investigate your issue.
So, please ensure you are sending tokens to the correct network.