Hello Archon,
- Just click on your building
- Then on the "Upgrade" button to upgrade it to level 21 or above.
Of course, the said building has to be at least level 20 !
The sketches icon displayed there is only to list the amount of required resources, as usual.
Up to level 20, you only need timber, bronze and grain.
From level 21 onwards, you need timber, bronze, grain and sketches.
If you're redirected to the market, it's probably becasue you don't have enough of one of them. Or because you clicked on the resource icon, instead of clicking on the "upgrade building" button.