As a lead booker, when creating a court booking with 'pay your part' - Nettla first reserves the full court cost on your account. This is to guarantee the income to the club in case other players do not pay their part.
Due to the reserve-charge-later mechanism, that causes club wallets to sometime not be applicable for specific cases. This case occurs when the 'full court cost' is larger than your current balance in your club wallet. Nettla is unable to 'reserve an amount' with a combined payment method of wallet + card.
Example:
Your wallet has £20
You are the lead booker (creator) of the court booking
Your share is £8
But the full court cost is £32 (the amount we need to hold on your account)
Since £20 doesn't cover £32, we can't use your wallet, even if it covers your share of the court
What you can do instead:
Pay by card for this specific booking
Create or join a public or private match using your wallet
Join someone else's booking using your wallet