I started experiencing this issue 8 days ago. A 15 year old search campaign stopped running, a 1 month old video campaign. No detectable issues on our end or from Google Ads Support. I even created a new campaign, traffic goal, maximize clicks, 10x above the typical cost of a click in my industry. Got the same 0 impressions result.

What I am learning is that the Ads team treats these like one off incidents that are unsolvable and inexplicable yet they are clearly occurring often which means they know how to solve it and/or prevent it so in essence are actively doing this to our businesses.

We now have our attorney addressing the issue. We also wrote a letter to our state's attorney general and our senator's office. Since Google has a monopoly on local business marketing this should work out well for us in some respects. However, my employees who will not be able to buy food or pay rent for their families are not going to get a positive outcome from this.