[Observium] The system doesn't show graphics

I installed Observium on Ubuntu server. I followed all instructions available on the Observium web. However, the system doesn't show any kind of graphics. Also, I want to add a new Linux device with snmp v2 client installed, the system can't reached with the v2c features. Finally, I attached a screenshot of the linux server I could add it using CLI.

Any ideas?

TIA

--