[Solved] Invoice Amounts Not Updating

I just installed InvoicePlane and love the feature set and customizability. However, when I create and save an invoice, the Subtotal, Item Tax, Invoice Tax, Total, Paid, and Balance amounts are not updating. The per item amounts are fine, but the overall amounts are still $0.00. This appears on the invoice page, email templates, invoice list, and guest URL.
What am I doing wrong?

Please see https://forums.invoiceplane.com/discussion/44/subtotal-item-tax-etc-field-not-updating for further error discussion.