I have troops to promote. But when I go to do it they're not showing up. I know I have them since ..

If those troops are out gathering, they are not available for upgrade.

Have you selected the correct lower tier? It should show how many troops you have available for that tier on the top right above the stats.

It will only list troops that are available to use right now. So if your troops are wounded or out gathering or marching anywhere then they won't be listed. You need to wait for them to return of be healed before you can promote them. If you have been attacked they could also have been killed.