To claim a lootbox won from staking FITFI you should have FITFI in your wallet to pay for the network fees. If you have enough for fees, please try to take these steps before reaching out to our support team:
Log out and log in from the staking account,
Disconnect the wallet you use and connect again,
Log out, clear cookies and cache,
Turn off ad blocks and anti-tracker browser extensions,
Use another browser,
Use incognito window.