We realized there was a change from uImage to zImage between versions and managed to update that in the environment as you can see below, but it still will no longer boot 2.7 from the uImage!
U-Boot 2016.11-2.7.6+g52259cf (Apr 24 2019 - 17:43:56 -0700)
CPU: Freescale i.MX6DL rev1.1 at 792 MHz
Reset cause: POR
I2C: ready
DRAM: 512 MiB
PMIC: device id: 0x10, revision id: 0x21, programmed
MMC: FSL_SDHC: 0, FSL_SDHC: 1
auto-detected panel vga-rgb
Display: vga-rgb (640x480)
In: serial
Out: serial
Err: serial
Model: Toradex Colibri iMX6 DualLite 512MB IT V1.0B, Serial# 04941907
Net: using PHY at 0
FEC [PRIME]
Hit any key to stop autoboot: 1 \0x08\0x08\0x08 0
Booting from internal eMMC chip...
reading imx6dl-colibri-eval-v3.dtb
45188 bytes read in 17 ms (2.5 MiB/s)
reading zImage
** Unable to read file zImage **
emmcboot failed
switch to partitions #0, OK
mmc1 is current device
Scanning mmc 1:1...
switch to partitions #0, OK
mmc0(part 0) is current device
Scanning mmc 0:1...
starting USB...
USB0: Port not available.
USB1: USB EHCI 1.00
scanning bus 1 for devices... 4 USB Device(s) found
scanning usb for storage devices... 0 Storage Device(s) found
scanning usb for ethernet devices... 0 Ethernet Device(s) found
USB device 0: unknown device
BOOTP broadcast 1
DHCP client bound to address 192.168.222.139 (7 ms)
Using FEC device
TFTP from server 192.168.10.1; our IP address is 192.168.222.139; sending through gateway 192.168.222.1
Filename 'boot.scr.uimg'.
Load address: 0x17000000
Loading: *\0x08T T T T T T T T T T
Retry count exceeded; starting again
Colibri iMX6 # printenv boot_file emmcboot
boot_file=zImage
emmcboot=run setup; setenv bootargs ${defargs} ${emmcargs} ${setupargs} ${vidargs}; echo Booting from internal eMMC chip...; run emmcdtbload; load mmc 0:1 ${kernel_addr_r} ${boot_file} && run fdt_fixup && bootz ${kernel_addr_r} ${dtbparam}
Colibri iMX6 # setenv boot_file uImage
Colibri iMX6 # saveenv
Saving Environment to MMC...
Writing to MMC(0)... done
Colibri iMX6 # reboot
Unknown command 'reboot' - try 'help'
Colibri iMX6 #
U-Boot 2016.11-2.7.6+g52259cf (Apr 24 2019 - 17:43:56 -0700)
CPU: Freescale i.MX6DL rev1.1 at 792 MHz
Reset cause: POR
I2C: ready
DRAM: 512 MiB
PMIC: device id: 0x10, revision id: 0x21, programmed
MMC: FSL_SDHC: 0, FSL_SDHC: 1
auto-detected panel vga-rgb
Display: vga-rgb (640x480)
In: serial
Out: serial
Err: serial
Model: Toradex Colibri iMX6 DualLite 512MB IT V1.0B, Serial# 04941907
Net: using PHY at 0
FEC [PRIME]
Hit any key to stop autoboot: 1 \0x08\0x08\0x08 0
Booting from internal eMMC chip...
reading imx6dl-colibri-eval-v3.dtb
45188 bytes read in 17 ms (2.5 MiB/s)
reading uImage
5018072 bytes read in 185 ms (25.9 MiB/s)
emmcboot failed
switch to partitions #0, OK
mmc1 is current device
Scanning mmc 1:1...
switch to partitions #0, OK
mmc0(part 0) is current device
Scanning mmc 0:1...
starting USB...
USB0: Port not available.
USB1: USB EHCI 1.00
scanning bus 1 for devices... 4 USB Device(s) found
scanning usb for storage devices... 0 Storage Device(s) found
scanning usb for ethernet devices... 0 Ethernet Device(s) found
USB device 0: unknown device
BOOTP broadcast 1
DHCP client bound to address 192.168.222.139 (4 ms)
Using FEC device
TFTP from server 192.168.10.1; our IP address is 192.168.222.139; sending through gateway 192.168.222.1
Filename 'boot.scr.uimg'.
Load address: 0x17000000
Loading: *\0x08T T T T T T T T T T
Retry count exceeded; starting again
Colibri iMX6 #