Sixfab LTE Hat not powering on with a stacked hat configuration

Hi,

It appears that my Sixfab LTE hat cannot power on when I have the Sixfab LTE hat stacked with a second hat. My system is based on a Raspberry PI 3B.

Here are the diagnostics:

pi@LG-WS2:~ $ uname -sr
Linux 5.10.17-v7+
pi@LG-WS2:~ $ lsusb -t
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 1: Dev 3, If 0, Class=Hub, Driver=hub/3p, 480M
|__ Port 1: Dev 5, If 0, Class=Vendor Specific Class, Driver=lan78xx, 480M
|__ Port 2: Dev 4, If 0, Class=Vendor Specific Class, Driver=usbfs, 480M
|__ Port 2: Dev 4, If 1, Class=Vendor Specific Class, Driver=, 480M
pi@LG-WS2:~ $ ls /dev/ttyUSB*
ls: cannot access ‘/dev/ttyUSB*’: No such file or directory
pi@LG-WS2:~ $ dmesg | grep tty
[ 0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=1 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 bcm2708_fb.fbwidth=1600 bcm2708_fb.fbheight=1200 bcm2708_fb.fbswap=1 vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000 dwc_otg.lpm_enable=0 console=tty1 root=PARTUUID=698e33bd-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles
[ 0.000375] printk: console [tty1] enabled
[ 3.021687] 3f201000.serial: ttyAMA0 at MMIO 0x3f201000 (irq = 114, base_baud = 0) is a PL011 rev2
[ 3.024839] 3f215040.serial: ttyS0 at MMIO 0x3f215040 (irq = 86, base_baud = 50000000) is a 16550
pi@LG-WS2:~ $ sudo cat /sys/kernel/debug/usb/devices

T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 1
B: Alloc= 0/800 us ( 0%), #Int= -1, #Iso= 0
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=01 MxPS=64 #Cfgs= 1
P: Vendor=1d6b ProdID=0002 Rev= 5.10
S: Manufacturer=Linux 5.10.17-v7+ dwc_otg_hcd
S: Product=DWC OTG Controller
S: SerialNumber=3f980000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=256ms

T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=480 MxCh= 4
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=02 MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=2514 Rev= b.b3
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=01 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=09(hub ) Sub=00 Prot=02 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms

T: Bus=01 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=480 MxCh= 3
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=02 MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=2514 Rev= b.b3
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=01 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=09(hub ) Sub=00 Prot=02 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms

T: Bus=01 Lev=03 Prnt=03 Port=00 Cnt=01 Dev#= 5 Spd=480 MxCh= 0
D: Ver= 2.10 Cls=ff(vend.) Sub=00 Prot=ff MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=7800 Rev= 3.00
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I:* If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=lan78xx
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=83(I) Atr=03(Int.) MxPS= 16 Ivl=1ms

T: Bus=01 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#= 4 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0bda ProdID=2838 Rev= 1.00
S: Manufacturer=Realtek
S: Product=RTL2838UHIDIR
S: SerialNumber=00000001
C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=usbfs
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 1 Alt= 0 #EPs= 0 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
pi@LG-WS2:~ $

The Sixfab Hat powers on fully once I remove the second hat from the stack. Any suggestions on next steps would be appreciated? My previous instances based the Quecel modems (vs the Telit I just purchased) worked well in this configuration.

Thanks,

Dustin