Hmm, do you mean when you click on "Help"/"Gimp Online" and can select from 'Developer, Main, Plug-in, User Manual' ?

Mine seems to work but then I've already got my browser open and have had Gimp installed for years.
I'm not sure if there is a setting to use a certain browser or not but in any case, none of this should keep you from using the Software.

You might want to close Gimp and restart it and try again. Sometimes you have to do that with Gimp for certain settings to take effect but this is just a guess.

If you really need those links here they are:
GIMP Developer Resources - GIMP Development
GIMP - The GNU Image Manipulation Program
GIMP Plugin Registry | A repository of optional extensions for the GIMP.
GIMP Documentation

The user manual links are:
2. Main Windows
Chapter 6. Getting Images out of GIMP
14. Drawing Simple Objects
Appendix D. Eeek! There is Missing Help
2. Preparing your Images for the Web
5. Paths
Chapter 10. Enhancing Photographs

As far as I know there is no real "Online" version of Gimp but I hope something here is helpful because I know how frustrating it was when I first started trying to learn how to draw digitally. Just be determined not to give up and you will get there.