General Description: Why are the parts not programming when the software detects them in the chain?
ISP operations can require a substantial amount of current for extended periods during "verify" (100mA for 5 seconds). If the power supply of the system cannot support this, the "verify" will fail.
Programming also requires a larger amount of current, although the program pulse current requirement typically lasts only 10ms to 100ms. ISP operations such as program and verify will not correctly operate with high impedance voltage sources, or micro power supplies.