Hello, I am working on a custom board that has Kinetis K28F (MK28FN2M0AVMI15) on it. The platform that we are developing software is MCUXpresso IDE V11.0.1.We are at the beginning of the software development process; therefore, we are still trying to use SDK examples provided for the FRDM-K28F development board as a template. It was working fine that we could successfully verify our boards by using PEMicro Multilink but we could not program the flash by using GUI Flash Tool. I thought it is because the oscillator frequencies of our board and the FRDM board are different and I modified the clock settings of the SDK 2.6 Led Blinky example. I changed the oscillator frequency to 24Mhz and the mode to HighGainMode inside the clock_config.c file. I also added an oscillator feedback resistor to my board. Then I could program my board and observe the oscillator output by scope. It was good until here but then I can no longer connect to the board. When I try to debug them in MCUXpresso I get the messsage "An error occured while connecting to the interface hardware or target specified in the Launch Configuration Dialog. For this launch, you may retry/re-specify the connection with the following parameters:" I can still successfully connect and debug my other boards whose flash is not programmed yet. Do you have any suggestions about this issue?