Unable to Install Insync on Zorin Pro 16.3

As I couldn't find this package in the default repositories I assume you followed Insync's download instructions to install it?

If so, you may have used the wrong codename to use for Ubuntu. ZorinOS 16.3 is based on Ubuntu 20.04 and thus the codename to be used should be "focal" (no need to write it as "focal-fossa" or anything). With this, I can install it normally:

My file looks like this:

cat /etc/apt/sources.list.d/insync.list
deb http://apt.insync.io/ubuntu focal non-free contrib

Try to update this file to show as mine and test again.