Today we have a different error when trying to save a Sales Order that should have a total of "0", but Method believes is negative and it won't sync with Quickbooks. Attached is a screenshot as an example. It has to do with the point as which sales tax is counted towards the Sales Order total.
As you can see, if it added the sales tax to the total before it tries to save the sales order, it should be a sales order of size "$0.00". However, because it does not count the tax until later, it believes the SO total is negative.
I am already in contact with support.