Can you elaborate a bit on what you mean by 'all the patches sound equal'? Do you mean they all sound similarly poor (fizzy, scratchy, low volume, noisy, ....) although you can detect a basic difference when you switch patches? Or do you literally mean all patches sound exactly the same - in other words you can't tell any difference in the sound when you change patches (in this case the patch might actually sound good, but they all sound identically good).
If it's the latter case (all patches actually sound identical) it could simply be that you have Tone 2 Locked, and your patches only use Tone 2. To make sure Tone 2 is unlocked, check the padlock icon in the bottom row of the Home page display; turn the little knob beneath the icon until it shows unlocked.
But if it's the former case please provide more detailed information about the bad sound you are hearing.