AR: Error Generating Invoice From a Sales Order

I’m getting the following error when trying to generate invoice from a sales order. It appears to be failing when calculating sales tax.

Error: Order SO-###### (6012): Only in progress transactions can be updated.

Call Stack:

[s] \Classes\STOTaxCalc\processMessages 54

[s] \Classes\STOTaxCalc_Sales\calculateTax 177

[s] \Classes\STOTaxCalc\calcTax 9

[s] \Classes\STOTaxCalc\RunTaxCalc 10

[s] \Classes\TaxSales\calc 45

[s] \Classes\SalesCalcTax_Sales\calcTax 32

[s] \Classes\TradeTotals\jsCalculateTax 10

[s] \Classes\SalesTotals_Sales\jsCalculateTax 17

[s] \Classes\TradeTotals\calc 120

[s] \Classes\TradeTotals\calculateTotalAmount 6

[s] \Classes\TradeTotals\tax 5

[s] \Classes\SalesInvoiceJournalCreate\calcLineAmountExclTax 9

[s] \Classes\SalesInvoiceJournalCreateBase\createJournalLine 44

[s] \Classes\SalesInvoiceJournalCreate\createJournalLine 9

[s] \Classes\FormletterJournalCreate\createJournalLines 24

[s] \Classes\SalesInvoiceJournalCreate\createJournalLines 7

[s] \Classes\FormletterJournalCreate\createJournal 19

[s] \Classes\FormletterJournalCreate\run 6

[s] \Classes\SalesInvoiceJournalCreate\run 12

[s] \Classes\FormletterService\createJournal 29

[s] \Classes\FormletterService\run 91

[s] \Classes\FormletterService\postSalesOrderInvoice 14

[s] \Classes\DictClass\callObject

[s] \Classes\SysOperationServiceController\runOperation 93

[s] \Classes\SysOperationServiceController\run 27

[s] \Classes\FormLetterServiceController\run 3

[s] \Classes\SalesFormLetter\run 90

[s] \Classes\SalesFormLetter_Invoice\run 6

[c] \Classes\SalesFormLetter\main 100

[c] \Classes\FormFunctionButtonControl\Clicked

[c] \Forms\SalesTable\Designs\DesignList\buttonUpdateInvoice\Methods\Clicked 9