I assume your /etc/rc.local file does not contain the literal quotation marks that you surrounded your command-line with in your question. If so, remove them; they are the problem.
I also assume you've used the search feature in htop to confirm that the process is definitely not running. If you only look at the default view, htop sorts processes according to how busy they are. It's possible your script is running but is blocked for some reason (such as waiting for input). If so, it might not show up near the top of your list.
If your script is definitely not running, or if it is running but not doing whatever you want it do do, one debugging tip is to capture the output and error messages into a file so that you can read it after it has run and (presumably) failed. Note that the syntax is very particular. Don't use quote marks, and make sure you preserve the spaces as follows.
sudo /usr/bin/python /home/smart-scale/scoreboard/main.py > /tmp/scoreboard.log 2>&1 &
The first part of the command has your original command line, minus the & at the end.
The > /tmp/scoreboard.log part is a shell redirection and it causes any printed output from your program to be captured (redirected) to a file called /tmp/scoreboard.log. I made up that name, you can change it to whatever you like. It should be a complete fully-qualified file path, though.
The 2>&1 part is a different kind of redirection that causes error messages to also be captured in the same file as the output messages, in order of occurrence with the output messages.
The final & puts the command in the background just as you had in your original command line.
Reboot and use nano, cat, or less to check the contents of the file /tmp/scoreboard.log. With luck it will tell you what is wrong and you can correct it. If you don't understand what the output means, update your question with the output and we'll try again.
P.S. Note that this debugging command is for troubleshooting only; if you leave this change in indefinitely, you might fill up your disk with logging data.
P.P.S. A couple other comments that probably have nothing to do with your problem.
First, the use of sudo in /etc/rc.local commands is not needed, as everything run from rc.local is already run as root. It's harmless to leave in, but I recommend removing because later on you may wonder why it's there.
Second, you don't need #!/usr/bin/python (which is called a bang path) in your python script file since you are explicitly calling /usr/bin/python on the command line. You could remove the bangpath from the python script, or you could leave it in and remove the explicit call to /usr/bin/python in the rc.local script. If you do the latter, you have to make sure the script it executable (chmod a_x /home/smart-scale/scoreboard/main.py). If all of that is new to you, don't worry too much. Leaving it as-is is not hurting anything, and in fact is quite common. I just wanted to let you know they are two different ways to get the same effect, i.e. to get your script run by a python interpreter.