This morning I had the same Issue as in this thread. I had 7 Updates, but the "Updates" tab was empty. The "solution" seemed to be updating on the "Purchased" tab.
But my tab says, that I haven't purchased any apps yet.
I am logged in....
I moved from Germany to America. But I have downloaded several Updates for Xcode in Germany, as well as in America.
I have changed my "Country and Region" to the States. And I just have tried to change it back. The tab stays empty.
I want to update to Xcode 8.1
Now I'm downloading Xcode as if it would be a complete new app. It asked me to "get" instead of "update" Xcode...
Even tho I have it installed.
I have tried to switch back to the German Store by changing back my "Country and Region". And I have restarted my MacBook 100 times. Also, I only use this one AppID.
First Xcode download was in Germany a year ago. But update to macOS Sierra, what also brought me Xcode 8 was with this Account and with the US App Store... So it should not be a matter of Country/Region...
PS: The updates issue is gone since I have activated Auto Update.. I have no pending updates anymore.
But Xcode is still in Version 8.0 and I'm able to "download" (get) Xcode 8.1 from the store.