Fitcash is automatically applied during checkout so it’s quite possible that you didn’t notice when it got used. Please check the Fitcash ledger which shows date wise details of earnings and spends.
Simply head to your profile > Account > Fitcash.
Please also note that you can earn fitcash reward for cult/mind.fit classes maximum once per day and only if your attendance is marked. Even if you have attended 2 classes, you will get a reward only once. Likewise, you only get fitcash on eat.fit orders that were successfully delivered for orders above Rs 99 (excluding packaging charges and any Fitcash used for payment)