Chris,
I've absolutely reproduced this error. It is very frustrating. I combine revenue data from 6 different sources including Quickbooks Online (QBO). Its worked for months. I've had to add another revenue stream to the report and now the QBO authentication/re-authentication dialog is blank and I can't proceed, and therefore can't publish my updates. I've tried clearing credentials and re-entering. I've opened up a ticket with MS Support and will keep you posted.
I think the December or February Power BI Desktop update broke the connector. Not sure without further trouble-shooting. The QBO connector is weak in its current form as it forces you to select the company within the account. There is no support for multiple companies within one pbix file.
I'm experimenting going further upstream to Data Azure Factory to stage data, but now there is a disconnect between Microsoft's OAauth1 support for the connector and QBO now only supporting OAuth2, UGH....QBO Product Team, please stabilize this data connector.