[Discuss-gnuradio] GNU flow graph containing a UHD block - unable to detect USRP E310

I have an E310 device connected over an Ethernet link to a laptop running GNU Radio.

When I attempted to execute a GNU flow graph containing a UHD block, I got the following error:

RuntimeError: LookupError: KeyError: No devices found for -----> Empty Device Address

I have entered the device IP address in the UHD block.

I can ping the E310.

Any help much appreciated.