KeyError: 'Split Type'
This turned out to be due to two bad lines written to the top of each file. Removing those led to additional errors, “KeyError: 'Account Name'” and “KeyError: 'Transaction Id'“.
In the end, I had to load the CSV file into a spreadsheet and perform the following steps:
Delete a few lines at the top, which list the account name.
Add column “Account Name”, populate it with the name of the account.
Add column “Transaction Id”, populate it with an incrementing list of numbers.