M4100-50G-POE+ sFlow with PRTG. Has anyone done this?

Thank you schumaku for pointing that out.

nsskyetech I reviewed your configuration and what appears to be lacking is the sFlow Source Interface. By default it is VLAN 1, but for whatever reason this has become non routing. You will need to create either a VLAN routing interface or physical routing interface for SFlow.

Below is where you can configure this in the web UI:
for VLAN routing interface: Routing - VLAN - VLAN routing 
for Physical routing interface: Routing - IP - Advanced - IP Configuration (to enable Routing mode) then IP Interface Configuration

Once this has been configured select the routing interface under Monitoring - sFlow - Basic - sFlow Agent Information - Source Interface or run the configure command "sflow source-interface <slot/port or vlan>"

Also, make sure that the receiver and source interface are able to communicate with each other. You can do a ping test from PRTG to the switch source interface to check this.

Lastly, I noticed that the firmware is very old, 10.0.1.16. I suggest to update the firmware to the latest which is version 10.0.2.35. Don't forget to backup the config first.

Have a lovely day,
RennaD
NETGEAR Team