It should show up if you are eligible for the upgrade. How about a screenshot of this? And please provide your system specs as well and include a description of you Windows 8 installation methodology (if applicable).
Not sue at this point but you obviously "look" eligible for the upgrade, and there have been many appropriate suggestions, so I can only guess there are probably two issues left to explore:
1. Maybe there is something in your configuration that is denying the ability to upgrade so how about supplying your system specs so we can have a detailed peek. Note that I seriously doubt this is the issue but we need to cover all bases here. However, normally any hardware issues are discovered ONLY after the upgarde is available and the process has been started.
2. I hate to think that this might be an issue but maybe you are not considered eligible because you (somehow) have your installation registered on more than one PC. Any chance that you (or someone else) used your installation disc elsewhere? Please understand that I have no idea whether or not this assumption may apply because it seems like you installation came pre-installed on your laptop but I just have to ask if there could possibly be an authentication issue here?
I've joined to share my workaround to installing 8.1 Final on top of the Preview if the Microsoft Store doesn't show the update as available.
My friend installed 8.1 preview on top of Windows 8 via the Store a while back and was running into the same issue where the Final of 8.1 wasn't showing on the store, it just reverted to the Home page (with facebook showing as a featured app). So We used the following link.. Write it in the address field in your Browser.