There can be a few reasons due to which you are not able to buy and sell. Please check if you have below mentioned error.

1) Margin Open Order

When you have a Margin Order which is in pending whether you are borrowing or lending you will not be able to buy or sell your token till your order gets executed or canceled. Sometimes small amount also left in Margin Open Order also gives this error. You can simply cancel the order from the Margin Page or from here https://bitbns.com/trade/#/activity/margin-openorder

2) Deposit Zone, Freeze Zone, and Liquidation Zone

When you are under Deposit, Freeze and Liquidation Zone while Margin Borrowing then also will not able to buy or sell your token. What you have to do is > Maintain your Worth Required Amount/Balance in your Bitbns Wallet. You can see it here https://bitbns.com/trade/#/activity/margin-ongoing-trades your Liquidation Price, Withdrawable amount, and Worth required. If you are in the mentioned zone you can simply Deposit the INR to your Bitbns wallet to come out of these zones and trade freely.

3) If you don't have margin and zone issues then your account must have been flagged.

Sometimes systems find unusual activity in the account and due to security reasons System Blocks the user fund to trade further and why? like Scammer got access to your account, Trade executed multiple times for single order and negative fund. You can simply raise the ticket for it and the agent will give you the solution for it. https://bitbns.freshdesk.com/support/tickets/new