Lumin requires a Lumin account. When I created one, I'd erroneously specified the wrong Google acct for "Login using Google" I didn't notice until I was ready to open a PDF file I had in my Downloads directory. But... The directory was there, but not the file. I did not see a way to change the Lumin acct to use the right Google acct, so I deleted it, and tried to create a new one. But this time, "Login using Google" no longer prompted me to choose a Google acct. The prior one was now hardwired.