My suspicion is that your installation of vuze on Xenial Xerus 16.04 is problematic. (Possibly you have used the snap packaging system which I confess to cordially disliking!)
Reverse whatever steps you have taken and remove your installed copy of vuze using the Ubuntu Software application, then follow the following steps in sequence:
1. Install some prerequisites:
Install the following by copying the entire code box and pasting into a Terminal window:
sudo apt-get install ca-certificates-java fonts-dejavu-extra java-common \
java-wrappers libbonobo2-0 libbonobo2-common libbonoboui2-0 \
libbonoboui2-common libcommons-cli-java libgif7 libglade2-0 libgnome-2-0 \
libgnome2-0 libgnome2-bin libgnome2-common libgnomecanvas2-0 \
libgnomecanvas2-common libgnomeui-0 libgnomeui-common libgnomevfs2-0 \
libgnomevfs2-common libjavascriptcoregtk-1.0-0 liblog4j1.2-java liborbit-2-0 \
libswt-cairo-gtk-3-jni libswt-gnome-gtk-3-jni libswt-gtk-3-java \
libswt-gtk-3-jni libswt-webkit-gtk-3-jni libwebkitgtk-1.0-0 \
libwebkitgtk-1.0-common openjdk-8-jre openjdk-8-jre-headless
2. Download and install vuze:
Use the bare Debian files rather than PPA magic, issuing the following 3 commands one at a time:
wget http://archive.getdeb.net/getdeb/ubuntu/pool/apps/a/azureus/azureus_5.7.5.0-1~getdeb1_all.deb
wget http://archive.getdeb.net/getdeb/ubuntu/pool/apps/a/azureus/vuze_5.7.5.0-1~getdeb1_all.deb
sudo dpkg -i *.deb
On my system this leaves vuze in a location that is easy to find:
andrew@corinth:~$ sudo find /usr -iname vuze
[sudo] password for andrew:
/usr/bin/vuze <-----------
/usr/share/doc/vuze
andrew@corinth:~$
The arrow of course is my own addition :)
3. Set magnet links to vuze:
Click on a magnet / torrent link in Firefox and if vuze is not an immediate option (competitor would be transmission) you can easily navigate to vuze and select this as the new default. See the screenshot below for this seen on my own system:

This worked easily on my Xenial system and hopefully will on yours as well :)
/snap/bin
? – muru Jul 23 '18 at 07:37vuze
, you can justwhereis vuze
. Files are just files, but an executable file has it's +x (execute) stat enabled. For examplewhereis ls
tells me its in/bin/ls
with manual for it in /usr/share/man/.... Astat /bin/ls
shows me the stats forls
, andfile /bin/ls
tells me the type of executable etc.... – guiverc Jul 23 '18 at 07:42