seems to have resolved itself
This issue has been resolved. Alpaca is migrating to a different internal authentication structure and several endpoints hadn’t been updated to recognize the new authentication. Paper trading portfolio history was one of those end points. This endpoint is called immediately when opening a paper account to render the equity chart. The end point didn’t authenticate so therefore asked to have the user login again creating an endless loop.
The status update can be found here.
Apologies for the inconvenience.