I have been getting the same error lately too, whenever I open a function like invoice, sales receipt or payment. I have let it run to see if it is just slow to open and it was 15 minutes before I just gave up and closed out. No other site was having issues loading so it looks to be a QBO issue. I have to close the tab and reopen, sometimes logging back in and sometimes not. That usually fixes it. I use Edge as it had had the fewest glitches of the browsers I have tried. It is frustrating to say the least.
