Trouble embedding level 4 emeralds

My hero has 1 lvl4 emerald and several lvl3 emeralds embedded. I try to embed another lvl4, but only lvl1,2,3 show up on the selection list. When I unembed the lvl4 then it shows 3 lvl4 emeralds, but as soon as embed 1, the selection doesn't even show lvl4. The other 2 lvl4 emeralds are still in my inventory. How can I get the other 2 lvl4 emeralds to embed?

Inventory or warehouse? If they are in your warehouse they won't show. You also need to remove the jewel in the slot you want to put the lvl 4 in first by clicking on it to open the space.