Hi @JBabichJapan / Twitter staff – finally getting around to revisiting this issue. I’d been patchwork manually editing campaigns in the Ads UI for the past couple weeks, but this is not ideal.
Today, about 90 minutes ago, I launched 2 new ad campaigns; the final step was unpausing them, same as the step 9 above.
Though they were not generating any impressions, they in fact hat servable = true and paused = false in their data when returned from the API (this is a combined return):
When, after an hour, neither had generated impressions, I tried hitting the endpoint to unpause one of them again. 30 minutes later, still no impressions.
The two IDs are 2whrm and 2whrl; I won’t edit them any further in case you’d like to see if you’re able to detect the problem with them.
Here’s my unpause request string:
{"method":"PUT","endpoint":"accounts/18ce53vvrko/line_items/2whrm","args":{"paused":"false"}}
And response from the API:

I’m pretty stumped by this, unfortunately 
Any help would be very appreciated!