This was happening to me also until today on one of our client's accounts. So to answer some of your questions, yes this would happen on all browsers/incognito and at different locations and networks. The workaround before was to change back to Facebook Classic but in September that was no longer a option. The other workaround was to go to facebook.com/home which did not exist and click on the home icon at the top then go to the business page shortcut on the left pane. Now it looks like Facebook just disabled the /business/dashboard page to display the same This Page Isn't Available message and click on the home icon etc... to bypass. Here is the last monkey wrench for you. If you go to account settings and Ads the settings tab will just flicker and eventually just say that facebook has closed the connection in the settings tab. You can click on the home icon at the top to get off the page. Other than that it looks like Facebook fixed the issue through obscurity which is not the best way since it does not fix the root issue which is that Facebook's backend web hosting systems created a redirect loop which could be just a couple of bad lines of code that created it. Just as a final note, our client's account is classified as a Gray Account which might have some other unforeseen consequences because of that.
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