When a pyranometer is not updating data you can follow on site the next steps:
1. Near the pyranometer find the junction box.
On this junction box you should distinguish the pyranometer side and the controller side.
The pyranometer side is where the pyranometer cable is connected.
In the controller side the power and data cables coming from controller are connected.
2. Measure on the junction box between white and black.
The voltage should be 24 VDC. If not, you should check continuity of the cable (between substation and junction box). You should also check inside Inaccess panel if the power supply unit is operational.
3. On the junction box from the pyranometer side the data cables are the yellow (data+), grey (data-).
You should find from the controller side the cables that are connected with yellow and grey. Disconnect the cables (coming from the controller side). Measure the voltage between them).
It should be 5VDC.
If it is 0, check the continuity of the cable (between controller and junction box). If cable is fine you should contact Inaccess in order to find out from the panel's side what is going wrong.
Please refer to the below photo from a site case and to the screenshot of Kipp&Zonen manual
Figure 1. Kipp&Zonen junction box
Figure 2. Kipp&Zonen manual