First of all, you have to know what does the Yocan UNI Pro no atomizer error.
When the device can't detect the cartridge, it will alert no atomizer error.
So, you have to make sure firmly connected, adapter and cartridge.
Here are some tips for your refer to.
1. Use a q-tip to clean the contact points.
2. Install a brand new adapter or cartridge. Sometime the older part can't connect very firmly.
3. Pull out the contact point a little.
4. It's still can't working after above tips, please contact the head shop you bought it from.