Coin deposits require a certain number of on-chain network confirmations which depend on the network, hence deposits may not be immediately available.
For example, an FTM transfer via the Fantom network will require 1 confirmation to be deposited to your wallet and 5 confirmations before the amount can be withdrawn.
These details can also be found in the deposit section of your account.
You can also use the relevant explorer of the network used to track the status of your transaction (e.g. https://ftmscan.com/ for transactions on the Fantom network).
Additionally, you will receive an e-mail confirmation when a coin deposit has been received in your Felix account.