The certified CryptoTax software checks each transaction whether the stock of the corresponding account is sufficient to serve the exit of the coins. If "over stock" is sold or paid - i.e. more than actually available - this is an indication that the transaction history is not complete or incorrect.
Since for tax purposes a complete and correct transaction history is essential for the calculation of acquisition costs and times, it is strongly recommended to supplement the missing history or to correct any import errors before creating the report.
In this case, the missing history area will show you which transactions are affected. You can also see how much of which asset is missing to serve the transaction.
To solve the problem please check the completeness and correctness of your history and add missing trades to the corresponding account. Here you can find out how to do this.