Since the last Spotify update (Current version: 184.108.40.206368.gbd68dbef) you are not able to launch Spotify with different user accounts on your mac. The error message in the title is the result. There are two different solutions for this problem: You can reinstall Spotify every time you switch user (for example via brew) or you set the right rights in the filesystem. Reinstalling spotify every time is not the right way and can be pretty annoying. Setting the right rights is a better approach.
On every Mac there is a group called „everyone“. Every user account is in there so it would be nice when Spotify would be started if the user is in that group. You can easily achieve this with two commands in the terminal:
:~$ sudo chown -R $USER:everyone /Applications/Spotify.app :~$ sudo chmod -R 775 /Applications/Spotify.app
You are asked for your sudo-password at the first command. This should be the same password as your login password. If that’s not going to work out for you then you are not an admin on that Mac. Please ask your admin for help.
The commands explained: With the chown command you change the user and group membership of the Spotify directory in the filesystem. The currently logged in user will be set in the user part and „everyone“ as group. With the chmod-command the read, write and execute rights are changed so the current user and the group „everyone“ are allowed to do everything. Now every user can open Spotify again.
Maybe these steps have to be done again when the next Spotify update is released.