'Caffeinate' command not working in macOS mojave...

The Terminal command 'caffeinate' isn't working in macOS mojave. I've tried prefixing it with 'sudo' but that doesn't work either. I've also read online that the issue is perhaps to do with security/privacy measures in place by macOS.

Also, the only reason why I'm trying to use this command is that the Energy Saver settings in System Preferences aren't keeping the computer from sleeping/logging out. So if someone could offer a suggestion/solution that uses System Preferences to solve the issue, then I wouldn't even need to use the 'caffeinate' command.

More info: in Energy Saver, I have Display Sleep set to 2hrs and Computer Sleep set to 2.5hrs but the computer consistently goes to sleep after about 15-20mins. I have unchecked "Put hard disks to sleep when possible," and "Wake up for network access." However, I have reason to believe that the latter isn't working either as the computer always wakes up whenever I turn on my bluetooth speaker, which is annoying.

Does anyone have any suggestions to fix any of these issues?