Maintenance margin is the collateral required to keep an existing position open. It is set at 70% of the initial margin requirement. If your maintenance margin reaches 100% (as indicated in the Balance & Margin panel as well as in the top right corner of the Thalex trading interface), it means that you are in breach of the maintenance margin requirement.
In that case, you will lose control of your account as Thalex initiates its risk mitigation process. This process aims to remedy the maintenance margin breach and includes measures such as liquidations to reduce your risk exposure. During the risk mitigation process, you will not be able to enter any new orders and all of your open orders will be automatically cancelled.