Sometimes you may find that you can’t enter the Trade Mode to continue playing in it. In such cases, you will see a message that specifies the requirements. It can be a certain profit level that you need to achieve or a certain level in the Fight Mode. 

Check your Fight mode, paying attention to both the location name and the current stage number.

Once you achieve the necessary profit level or arrive at the required location or stage in Fight Mode, the Trade Mode will automatically unlock for you!