Updraftplus: 2.12.18.22
Wordfence: 6.1.14
Wordpress 4.6
I run a lot of sites and use WordFence on most of them and Updraftplus on all of them. I periodically check them all to make sure everything is up to date and take an independent backup.
I have just come across a scenario where I requested a backup in Updraftplus, the dialogue and user feedback was normal, the backup was created. When I switched to the backup view and attempted to download them the yellow bar that normally appears to indicate that the backup was being prepared did not appear.
As I had also just reconfigured the firewall in WordFence which is a quite recent addition, I suspected an interaction between the two. I deactivated WordFence and then went back to the backup screen and tried to regenerate them. They worked this time and I was able to download them.
I turned WordFence back on and it still works ok. I have not got around to checking any other sites yet, this happened this morning (22 Aug 16) with up to date code for everything.
I could not detect anything in the .htaccess file that might limit the functionality of Updraftplus while Wordfence was installed and running.
As I continue going around my sites if I see it again I will report it here. Right now the problem is resolved for me anyway.