Hello,
We have detected gifting activity on this account that matches using individual Steam accounts for commercial purposes.
Because of this, your account can no longer make gift purchases with Wallet funds. You are, however, welcome to continue purchasing gifts with other payment methods, and to use your Wallet funds toward making purchases for your own account.
Please note, that if you are using your Steam account for commercial purposes it's a violation of the Steam Subscriber Agreement and may result in the account being locked.
Because we have provided all the information we have for your issue, I'm closing this help request. If you have an unrelated issue, please open a new help request and we will be happy to help.
Steam Support
Sam