From what I can find it looks like there is a Quickbooks bug starting with QB 2018 that causes the Unregistered Quickbooks modal to be thrown even when QB is registered. The user can close the modal and log in to Quickbooks without issue, verifying that it is registered.
See this thread - https://help.developer.intuit.com/s/question/0D50f00004zoqaJCAQ/quickbooks-appears-unregistered-randomly
Because of this QQube won't refresh for me. As soon as I launch the synchronizer this popup is thrown, breaking the sync. The worst part is this doesn't happen every time the sync is scheduled. Sometimes it goes days running successfully. Other times, like today, the manual refresh has failed 10+ times in a row.
Thought I would check if others have run into this and found a work around.
As discussed in this guide: https://clearify.com/wiki/view/3691/error-80040427-unregistered-quickbooks running the QB File and Network Doctor should fix this issue.
However in your case it seems to be sporadic
It generally seems to be the proper port not being available - or possibly the internet cannot make a connection to the QB servers.
You might check to see if anything is attempting to use the same ports that QB uses.
See this Intuit Guide on Ports for QuickBooks Desktop: https://quickbooks.intuit.com/learn-support/en-us/access-data-remotely/set-up-firewall-and-security-settings-for-quickbooks-desktop/00/201468
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