Unlock tool network error

[joshuavaz_jv]

Please tell us some basic information before asking for help:
Model Name: ZE520KL
Firmware Version: OPR1.170623.026.WW_Phone-15.0410.1807.75-0
Rooted or not: NOT
Frequency of Occurrence: Repeatedly
APP Name & APP Version (If your issue relates to the app): Unlock device tool (UnlockTool_20180117(Andriod N/O) )
In addition to information above, please also provide as much details as you can, e.g., using scenario, what troubleshooting you've already done, screenshot, etc.
========================================
Please help me with this problem been trying for 2 hours now.
I noticed this is a common problem and gets solved by Asus.
Please help.

[victor010]

Hi, we'd request you follow the below steps:
1. Clear system cache.
2. Try the same under safe mode:
Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode
3. If still you face the issue factory reset your phone after taking a full backup.

[joshuavaz_jv]

Victor0_ASUS

Hi, we'd request you follow the below steps:

1. Clear system cache.

2. Try the same under safe mode:

Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode

3. If still you face the issue factory reset your phone after taking a full backup.

View post

Steps 1 and 3 done (forgot to mention that I had already tried factory reset)
How will step 2 work? System unlock tool is 3rd party app and won't work in safe mode. (My device is not rooted)

I want to unlock bootloader to install custom ROM (its gotten laggy after 4 years)
Note: this is not my primary device and I have no data in it.

[joshuavaz_jv]

Tried installing app via adb on safe mode then rebooted to normal mode, still didn't work.