Mistakenly wiped system partition

[phoenix.505]

Device - OnePlus 5 (64GB), TWRP 3.3.1-0-20190713-codeworkx

Yesterday, while trying to reset my phone I accidentally wiped the system partition. I am able to boot the device into fastboot mode and TWRP (doesn't ask for any password), however the phone is going undetected on my Mac.
I tried ADB side loading using terminal, following error comes -

Device (Null) not found.

Tried to connect thru OTG, even that is going unnoticed. I just want to copy the ROM file to phone, in order to restore it to stock condition.
Any help would be appreciated...

 

[the_Nizo]

Was your device encrypted and you had a password? Otherwise it's normal that it doesn't ask for a password.

First off, I don't know how proficient you are.
I assume
- You're in TWRP
- Your phone is connected to your Mac and charges
- You're using a cable that can transfer data, eg. the Dash Charge cable

In TWRP, go to mount. You can either have MTP or adb enabled, not both at once AFAIK (MTP disabled = adb enabled). You probably have it disabled. You can either get the zip to the phone by MTP or via adb push. I think it happened once that I had to switch MTP off and on again.

If you try to use a USB stick, you have to mount it. You can do that under mount too. I'm currently not sure where it will be mounted though. (I don't know what formats are supported, but Fat32 should do the job).

I assume you tried sideload correctly, but just to make sure you did it right, you have to go to Advanced -> Sideload and enable it, THEN use the command 'adb sideload ....

If nothing of the above works, I only assume there's something wrong with the recovery. Try another version, official, codeworkx (he posted a thread), or blu_spark (latest version is on GitHub).
You can modify the system partition without needing to decrypt, doesn't matter.