If you are unable to map the trial balance, this will usually be due to not having applied an accounting structure. The guide below will take you through how to activate this.
 

The key identifier that no accounting structure has been selected will be that the lead schedule dropdown boxes will be greyed out. 

To apply an accounting structure;

1. Select Tools from the Trial Balance page:
2. Select Map Accounting Structure (Industry Template) or Map Accounting Structure (Custom Template) if your firm is using a custom structure.
3. Select the relevant accounting structure based on the source your account codes come from;
4. Once selected, the Accounting Structure will then load onto the Trial Balance.
5. The Trial Balance will then be auto mapped or allow you to manually map the accounts.