Core problem summary
Failed attempts:
Why this works: In-circuit programming (ICP) fails when other components on the board (capacitors, resistors, another IC) share the SPI bus. Desoldering isolates the chip. Core problem summary Failed attempts: Why this works:
This is the most common cause, especially when using an SOIC8 test clip. Open NeoProgrammer
Basically, the data on the chip doesn't match the buffer/file after writing/verifying. Basically, the data on the chip doesn't match