Following a blankflash, you can only boot into the bootloader, which is normal. It seems that using a blankflash sets your bootloader to be locked, regardless of if it was previously unlocked in the first place. Provided you can flash a stock ROM, your bootloader should become unlocked again.
Have you tried flashing the April 2018 fastboot stock ROM from
https://forum.xda-developers.com/moto-g4-plus/how-to/stock-rom-npjs25-93-14-4-march-1-t3608138 ? The guide there should be useful in how to reflash stock firmware to your device, and as it's the newest firmware that has been leaked, should rescue your device.
If you want to keep your bootloader unlocked and try to save your data, then try the following flashing commands instead of the ones in the guide. Be aware that you may have to factory reset your device should it boot but be unstable.
These commands should flash the April 2018 GPT, bootloader, system and modem to your device. Please try to avoid hardbricks in the future by only flashing stock firmware as new or newer than your bootloader, and please do not use old OTA updates.