Hello,
I hope all is great with you.
You are correct, unfortunately the SGTL500 device does not have a reset pin.
In this case, the preferred supply sequencing is VDDIO/VDDA (it does not matter which comes first) and then VDDD. So, I do recommend to perform some tests using the VDDIO/VDDA supply rails.
I hope this information helps.
Regards,
David