Dell XPS 9520 Sleep

I believe I have sleep configured according to Support for the S0ix sleep state · Issue #6411 · QubesOS/qubes-issues · GitHub.

I can suspend, and wake from suspend

However /sys/kernel/debug/pmc_core/substate_residencies always says 0.
Substate Residency
S0i2.0 0

qvm-features dom0 suspend-dom0-s0ix is enabled

/sys/power/mem_sleep
[s2idle]

/sys/kernel/debug/pmc_core/substate_residencies shows several items without a Yes under Live Status. Is that the reason substate_residencies always says 0?

I only have one USB controller in sys-usb. (No Thunderbolt devices).

I regularly use a Dell WD19 dock for connecting an extra display, mouse, and keyboard.

S3 is not supported in BIOS.

I’m running Qubes 4.2.3 with testing updates.

How can I best troubleshoot this so that sleep will fully work?

Thanks,