Cube Programmer connects to target and programs, but STLink GDB says "No device found on target."

[SpinKernel]

I have a Mikroe Fusion for STM32 V8, I'm using the external DBG selection using an STLINK V3 plugged into the debug port. I can get Cube Programmer to load code onto my F302VC. When I load up STMicroelectronics ST-LINK GDB server. Version 6.0.0, I get the "No device found on target.".

Making sure it was hardware related, i tried a Nucleo-F302r8 and that works.

I've tried playing with the different reset behavior, specifying a stlink s/n, nothing seems to help. I assume its a problem with the fusion and the way its connected. Boot0 is grounded through a 10k. The only suspect i have is this MUX that switches between GPIO input and JTAG/SWD/TRACE. I'm still investigating. Hope someone else had this issue and has a solution!

Appreciate any advice!

[SpinKernel]

Probed the board, I don't think the MUX is the problem, the S pin is low which means the SWD pins are forwarded to the mcu. So very perplexed.

[SpinKernel]

I ended up using my Nucleo to program the Fusion board THROUGH the STLV3 (powered off, so i could use the STDC14 connector) and was able to enter debug mode just fine. Seems there's a problem with V3 and CubeIDE v1.8's GDB? I reloaded the firmware and didn't help. Also reinstalled CubeIDE 1.8, no dice. I've used this before to debug on a custom board so not sure what could be the issue. My guess the latest version of everything has a bug in it somewhere for V3 hardware.

[Tesla DeLorean]

The robustness and testing of this stuff continues to be lackluster..

[Tesla DeLorean]

Cross Posted Here https://community.st.com/s/question/0D53W000013JAxsSAG/stm32l462-not-found-stlink-v2-v3-in-stm32cubeide

[SpinKernel]

Yes, I was about to answer that one. Unfortunately your answer doesn't apply here. I DO see voltage, and the V2 DOES work (sorry I reread their post and realized they couldn't program or debug and it wouldn't let me delete my post). Everything points to a problem with the GDB 6.0.0 and V3. I don't understand what they broke because this has worked flawlessly back when it was V1.5 or 1.6 of the IDE. I have reinstalled everything, reflashed everything rebuilt all the configuration in the project. So far I have found nothing "wrong" other than V3 vs V2 STlink.

[HCohe.1]

I also found that STM32CubeProgrammer is more robust connecting to my board compared to STM32CubeIDE using the same V3 ST-LINK. In my case, I needed to reduce the SWD communication rate, listed as "Frequency (kHz)" in the IDE, to 8000 rather than letting it auto-detect.