I’ve just updated to the last version of xwiki (15.9) but I have this issue since some release. When we go to any user profile → Notification we get a “Failed to execute the [velocity] macro. Cause: [Encountered “” at xwiki:XWiki.XWikiUserSheet[line 64, column 5]” under email preferences. And we also notice that the “wheels” keep turnign under “Applications”. How can I fix those issues? Sorry for my poor English.
This sounds like you somehow broke some pages of the Notification Applications containing the macros for settings (probably during an upgrade). You can try to repair it but first you need to understand what pages have been modified: in Administration > Extension you can look for the installed extensions “Notifications Application” and “Notifications Macro”, and then perform “Compute changes” action on them, available when opening the menu by clicking on the arrow next to “uninstall”: