QuickBooks error 12029 happens when a user is unable to connect to the server. There could be several causes for the issue, but the most prevalent is that you are using an outdated version of QuickBooks. This is not the only issue that occurs as a result of this cause; there are other more, such as QuickBooks error 15270 and QuickBooks error ps033.
https://qberror006.com/quickbooks-error-12029/