I'm having the same issue on the similarly named sites. The problem is that PowerApps and Flow do not work on old/legacy BPOS (Business Productivity Online Services) sites. These site collections originally had microsoftonline in the URL.
Recently those sites were renamed by Microsoft to help allow the usage of the SharePoint App model.
As far as I've been told, if you want to use PowerApps and Flow, you need to have a site that does NOT include Portal1 in the URL. Those sites are housed on a different servert that is not compatible (and will most likely never be compatible) with PA and Flow.