Ubuntu 18.04 invisible mouse

I had Ubuntu 16.04 and suddenly I couldn't log in anymore. Each time I would try to log in, the screen went black and ask again for my password. I was stuck in a login loop. I updated to Ubuntu 18.04 and it fixed my problem, but now the mouse cursor is invisible. I can still click things, except I can't see the cursor.

I use Ubuntu with Parallels in my MacOs High Sierra.

This worked for me (apparently default mode is "touchscreen mode"):

gsettings set org.gnome.settings-daemon.plugins.cursor active false

On my system it was due to a broken upgrade,

Open the terminal with crtl-alt-t and run sudo dpkg --configure -a let it run until it stops; and then update with sudo apt update && sudo apt upgrade and reboot (sudo reboot if you can't use the gui to do that).

My cursor was back again.

dpkg with the --configure -a flags set will tell dkpg to configure any packages that have been unpacked but not configured.

apt update checks available repositories for any available upgrades, and apt upgrade tells apt to upgrade any packages that need it.