LAST EDIT AT END OF POST
We are using a custom board with an nRF51822 programmed with a modified beacon application (which worked several months ago). After opening MCP 3.4.0.8098 and selecting "Start Discovery" the error message "No command complete event received" occurs. Unplugging/replugging the J-Link and reloading MCB have not solved the problem. This problem was addressed in 2014 but I do not understand how the answers solve the problem.
I suspect an incorrect softdevice may have been programmed since this board has been used for both s110 and s130 projects. I opened nRFgo Studio 1.14.1.2369, browsed for s110_nrf51822_6.6.6_softdevice.hex and did and "erase all" followed by "Program" but the error "Unknown, fwid: 0x49" occurred. Unplugging/replugging the J-Link and reloading nRFgo Studio have not solved the problem. A fresh version of the softdevice has not been downloaded to verify that my copy is not corrupted.
I added the command line entries into uVision4 (eraseall, program_s110, program_s130). All three commands appears to run without errors.
Loaded MCP and after selecting Start Discovery the same "No command complete event received" occurred.
Installed nRFgo Studio 1.21.2.12 and now the FW is OK.
MCP 3.4.0 is still indicating "No command complete event". Will try the latest MCP version tomorrow.
Just installed MCP 3.10.0.14 but the same "No command complete event" error message occurs.
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P0.30 is open (no connection to ground). It may be impossible to solder a wire to the chip to make this connection but I will try.
However, it should be noted that this board has worked for months in the past and as recently as 2 weeks ago with P0.30 open.
I just found a note that I made over a year ago concerning the "No command complete event received" problem. It said that this error message will occur if an invalid UUID is inadvertently written into flash. The solution was to reload the softdevice which will also write a valid UUID (is this correct?). I have rewritten s110 several times using inside uVision4 under the Tools menu but the error persists. (Note: As stated above, I have been unable to write the softdevice using nRFgo Studio as I have done before. Is this all related?)