I have had a couple of other reports about this, and just got off a screen share with one such case. It was with a Mac user, which meant I couldn’t look at the developer tools to check for errors on the initial opening of that window, so I went ahead with the next test.
Instead of signing out, quitting, opening, signing in, I had him close the add location window, sign out, then open the add location window again. That triggered the sign in, he signed in, and then saw the add location intro slideshow for the first time. From then on the features worked ok.
After importing one site I had him quit SketchUp and open it again, so therefore still signed in. Opening add location worked fine. It seems like on the first use of add location it misreads whether you are signed in or not, but after it knows you are, things are good.
Aside from wanting to test with a Windows user, to look for the initial error, next chance I get I will have them try what Dave and Bryce were saying, sign out, sign in, then try add location. The difference is whether it was add location that initiated the sign in, and that may make a difference.
Hopefully we won’t get enough reports of this problem for me to be able to build up statistics! But, I’m ready with more things to try next time.