Hello Vieuxsage,
above anything else – the level III is not available yet.
If you want to upgrade your city you have to:
- fulfill all the needs,
- fill the beds in the house (11/11 on the level I),
- have enough resources stored,
- make sure the house isn't burning.
In the first screen all the needs are fulfilled, so you probably need to wait a few seconds. After the need gets checked it does not change the happiness immediately, the real happiness is calculated in time. If you waited and the happiness ratio is below 90, you should check tax ratios. Values above "Normal" will stop Huts from upgrading. So basically, if you have enough resources (including some water stored etc.) and the tax ratio is on the proper level, it might be a bug. Rember that you can check the upgrade state in the selection panel.
