At the top of the Dashboard tab, you can see three values that represent your account balance.
In the middle, you can see the committed balance. It is the amount of funds that has been assigned to your cards for upcoming payments.
On the right, you can see the available balance. It is the amount of funds that has not been committed on any cards, and is available to spend or assign to your cards.
On the left, you can see the total balance in the grey box. It is the total amount of funds you have in your Cledara account, and naturally, the sum of the committed and available balance.
If you are unable to top up a card even though you see there is enough total balance in your account, check to see if you have sufficient funds in the available balance. It could be that most of your total balance has already been committed on cards, and you are low on funds that are actually available to spend.
In this case, you could either top up your Cledara account or flush money out from each card manually to increase your available balance.