After looking over this issue nights and days, I finally have a solution. This solution was given by the MathWorks technical support.
This solution is for Windows computers
On the online, internet connected computer, follow the instruction as given above by the MATLAB Support Team.
Now, after transferring the files to your offline computer, follow the instructions below:
1. Make sure your Support Package folder is in the same hard drive as your MATLAB installation. If not, move it.
2. Open CMD
3. (In CMD) Make sure your path is on the same hard drive as your MATLAB installation drive. If not, change it by typing:
(to change it to D drive, for instance)
4. (In CMD) Change directory to your MATLAB folder, e.g.
cd “C:\Program Files\MATLAB\R2017b\bin\win64”
5. (In CMD) Type:
install_supportsoftware.exe -archives “<YOUR SUPPORT PACKAGE PATH>“
install_supportsoftware.exe -archives “C:\\SupportPackages\R2017b”
NOTICE: the path should end in the directory in which there exists an “archives” folder.
6. A new MATLAB window and an installation window should open.