If you have the app "HideUserAgent" installed, go to Setttings and under Connectivity click on Hide User Agent, then click Remove. after that you should be good to go.

HideUserAgent is an app that tricks websites into thinking that you're using a different browser or phone. That's why it affects the ovistore. If the ovistore thinks you're not using an n900 or other supported phone then it won't allow you to download any apps or say it's not available for your device.