Stuck at “critical software update is required” screen during startup

"At this point you need to wipe the drive and re-install your OS from an external OS installer drive.

First backup anything important off your drive (TimeMachine)

Next create a bootable OS installer using another Mac system, I personally would stick with Mojave for now as Catalina is still a bit buggy! In any case here’s how to create both:

How to create a bootable macOS Mojave installer driveHow to create a bootable macOS Catalina installer drive

Restart your system then using the Option key to enter into the Startup Manager select the USB-C installer drive. Once started go to the menu and select Disk Utility and then delete all of the partitions, then reformat the drive as one GUID APFS partition.

Reference: Mac startup key combinations

Now exit Disk Utility and start the OS installer letting it do its thing! Your system will reboot a few times and the screen will also go dark so don’t panic!!

In a few hours your system should have finished the OS install. Now before doing anything else apply all of the needed updates. Again, your system will reboot as Apple has updated the system firmware a few times depending which macOS you are installing.

Did that work?"

"I sh*t you not....a couple hours after posting this, my 2017 MacBook Pro 15 (A1707) booted up just fine, and the touchbar was working again. This is after 3 days of banging my head on the desk trying to figure out a way around it. I'm thinking the macOS 10.15.3 update had something to do with it, since it just came out and my system updated to it while in Safe Mode.

I do know for a fact what killed it was me wiping the entire drive (all partitions, including the one specifically set aside for the touchbar). It worked perfectly fine until I did this and then re-installed the OS. Why did I do this you ask? I just bought this MBP from someone on Facebook and I wanted to be sure I was starting from a completely clean slate.

Everything I read online says you should not wipe all the partitions on the MBPs with the touchbar, only the main OS partition. This totally smells like a software issue to me and not a hardware issue. Especially since mine was fine until I nuked all the partitions. Also, this site gave me a lot of insight into what I potentially did to create the issue. See the author's 6th attempt (Workflow 6):

The Untouchables - Apples New OS Activation for Touch Bar MacBook Pros"

"Hey guys,

I had exactly the same problem. This is what I did. I rarely shut down my computer, this time I thought I'll give it a rest. I had Samsung SSD and a WD MyBook Duo both plugged into the USB C ports. Although I have booted with the SSD before no worries, this was the first time with the MyBook Duo. I had the message come up on the boot up screen, I pressed shut down. Booted up again in Safe Boot (hold left shift until Apple logo had loaded half way, release) Got an access to the homescreen. Disabled Wifi and unplugged the MyBook Duo from USB C. Pressed restart and it booted up no worries. I think the culprit here might have been the external hdd. I'm not saying that this is the fix for everyone but if you're having a similar issue and have something plugged into USB C that you've never have before on a boot up, might be helpful to go through the process I did.

Hope somebody finds this useful"

"I got similar problem on 06 -01-2021. My macbook pro is 15 inch with touchbar. after a lot of research I was disheartened by reading many blogs where the logic board replacement solution was provided by apple and for many they had replaced their laptops which were covered under warranty.

However after a little bit of research I could conclude that the problem lies in the firmwere update for touchbar which is not in sync with the latest catalina update so when the laptop restarts it cannot find the firmwere for touchbar.

I believe some of the apple OS updates are not synched with the touchbar firmwere thats why this problem occurs.

And the supported firmwere patch is not reachable or is not available for the update.

I addressed this problem by logging in safe mode by pressing Left Shift Key during restart and then signing in to my apple account again and then installing the latest OS mac OS Big Sur version 11.1 which has enabled my touch bar again and also is not giving me any problems after reinstall.

I believe this OS comes with updated Touchbar Firmwere and thats how the problem is resolved.

Hope you guys find this solution helpful cheers."