MY20 Sync 3.4 Master Reset failed to blackscreem

Is the car under warranty?.
If so, I would contact the dealer.

I’m asking because a master reset should not cause a black screen…
…unless there’s something wrong with the unit (which the warranty would cover) or if the user did something (have you done anything?)…

Since your unit seems somewhat alive, check via forscan which theme do you have set.
This is the value you need to check → https://cyanlabs.net/asbuilt-db/sync3-apim/?search=Visual%2520Design%2520Variants%2520(VDV)%2520Sync%2520Versions%25203.0%2520thru%25203.4

Also, you not knowing which version the unit has does not really help.
You are saying the old one was 3.3 and the new one 3.4…
You could try creating an interrogator log to see if the unit produces the xml file, that will give information on what’s on the APIM. But the interrogator log is version dependent, so you will need to try many things.

From Tutorial: APIM Interrogator Utility/Create Interrogator Log

  • For Sync 3.0 version 1.0/2.2/2.3, use file GB5T-14G386-AA. (Released 2016-05-26)
  • For Sync 3.2/3.3 all versions, use file GB5T-14G386-AB. (Released 2018-10-11)
  • For Sync 3.4.18347 to 3.4.20237, use file GB5T-14G386-AC. (Released 2020-02-19)
  • For Sync 3.4.20282 to present, use file GB5T-14G386-AD. (Released 2020-10-07)