[Samsung Galaxy J7 Questions & Answers] CoperaN:
Some success.

Ok, guys, I've had a bit of progress with my device Samsung Galaxy J 7 Neo (SM-J701M- Android version 8.01)

On this phone, the option to unlock the bootloader was missing in Dev Opt and I knew that in order to achieve anything I was going to have to unlock the bootloader.

I searched and found that, via adb/fastboot (Google's Platform Tools) rebooting the phone to the bootloader you could enter the code: 'fastboot oem unlock' or 'fastboot flashing unlock' and voila! everything would be fixed...But...my device wasn't even being recognized by "fastboot" ! adb yes but no fastboot! Always the message: "Waiting on any device". Trying to find and install the drivers to do this was next to impossible.

It actually caused me soft brick my device. However, it was a blessing in disguise; I knew what had to be done, I was going to have to reinstall the firmware via Odin. I searched the site (Sammobile - you'll have to create an account.) and found the Oreo and the Pie Firmware, I downloaded both but played it safe and restored my device with the Oreo first.

And lo and behold the option to unlock bootloader was there! No hesitation, clicked that sucker fast!!

Now, I'm running PIE (No one has done a Custom ROM for this baby just yet) and with the unofficial TWRP in the first link below, it's a bit buggy but until they make an official one for us ... I guess we'll have to wait.

Oh! And don't forget to make a backup with Smart Switch!

And pay attention to the advice here:

1. Extract the firmware file you just downloaded. You should get 5 files:
AP (System &Recovery)

BL (Bootloader)

CP (Modem / Radio)

CSC_*** (Country / Region / Operator)

HOME_CSC_*** (Country / Region / Operator)

2. Add each file to its respective field in Odin v3.14.4. Use CSC_*** if you want to do a clean flash or HOME_CSC_*** if you want to keep your apps and data.
3. Reboot your phone in Download / Odin mode (make sure your device is off) with the following button combo: POWER + VOLUME DOWN + BIXBY
Other options in case first option did not work or isn't possible.

Option 2 VOLUME DOWN + VOLUME UP then USB cable

Option 3 POWER + VOLUME DOWN + VOLUME UP

Option 4 POWER + VOLUME DOWN + HOME BUTTON

Option 5 (Note9) USB cable + VOLUME DOWN + BIXBY

Option 6 (Note10) POWER + VOLUME UP

4. Once in download mode, connect your phone to the PC, preferably using the original USB cable you got with your phone. Odin should detect your device and a BLUE box will show up with the COM port number. (Be sure, the SAMSUNG-drivers are installed on your PC!)
Do NOT tick any extra boxes. The only options to be ticked are F.Reset Time and Auto-Reboot.
5. Click the start button, wait for Odin to say 'PASS' in a GREEN box. Once the flash is complete, your phone will reboot, and you can disconnect your phone from the PC

These are some of the links I found helpful:

https://unofficialtwrp.com/root-twrp-galaxy-j7-neo-sm-j701m/

https://www.androidexplained.com/galaxy-note-9-restore-firmware/

https://xdaforums.com/galaxy-j7/samsung-galaxy-j7-prime--j7-on-nxt-exynos7870/recovery-twrp-3-2-0-galaxy-j7-prime-t3716355

---------- Post added at 01:39 PM ---------- Previous post was at 01:30 PM ----------

I think that's because you have to be specific with the carrier; Orange; Nextel; Movistar...that makes a lot of difference in with the firmware. If you can, check to see what you had before and try that first.