It has not. We are still not at “cyberwar”
You know, what with me predicting the coup on November 9th, 2020 and you stating what is just now becoming readily apparent to a number of cyberwar experts, I think the SDMB needs to be on some sort of think tank payroll. 
Interesting tweet thread by Guardian (UK) contributing writer Carole Cadwalladr about how she has come to realize we have been in a cyberwar since 2014. Her ‘beat’ is Facebook and its disinformation platform, and she is involved in some organizations which combat Facebook’s anti-democratic malignancy.
There are some things which she is missing here, like the Gerasimov doctrine, but she is largely correct: Putin has been waging cyberwarfare against the United States (and the EU) for almost a decade, and everyone has ignored this obvious truth.
Well, most everyone. We didn’t.
https://www.politico.com/magazine/story/2017/09/05/gerasimov-doctrine-russia-foreign-policy-215538
With the war in Ukraine, found a long list of cyberwarfare ops being conducted against Russia by non-State actors. So maybe thats the answer: you don’t really ‘declare’ cyberwar, you just unleash the hounds of war.
Well, I don’t know that they were unleashed in that they weren’t really “leashed” in the first place.
There’s a lot of gray area as to what constitutes a cyber attack and by who. Which is one of the challenges, in that it often gives nations states plausible deniability as to their involvement.
Which also creates some gray areas around what the response should be. Particularly if the cyber attack has real world consequences (such as the alleged STUXNET attack by Israel on Iran’s nuclear program). For example, if a country tried to hack into a USN aircraft carrier during operations, is it justifiable to respond with a cruise missile to take out the wifi tower?
It can also be problematic if private companies like Microsoft or Google engage in counter-cyber attacks. Particularly if they are state-actors since you would now have private corporations engaging in hostile actions against sovereign nations, independent of US foreign policy.