Custom Target Debugging Issue

I have a custom board that has an STM32L476RG MCU with a LPC11u35FHI33/501 for the bootloader. I set this as my custom target on connection however when I try to debug I get the following error:

“Could not complete debug: Request reset failed with message: PyOCD failed to reset the target, please check the logs for more information”

Is this custom target configuration not supported?

I use the Nucleo-L476 target for compiling and that works for creating a .bin that I can flash via the manual drag and drop method.