For past couple of months, that's how much I saw Destiny 2. That isn't much. Darn!
Actually, there is an Internet full of people having the same problem. There are various solutions to, which have worked for some people and for some, not so much.
After doing all the possible things, including throwing dried chicken bones to a magical sand circle, I ran out of options. I had to escalate the problem to Blizzard Support. Since this wasn't a paid game, obviously it didn't reach their highest priority queue. But ultimately the cogs of bureaucracy aligned and I got the required attention to my problem. But ... it was unsovalvable. Or it seemed to be one.
Today, after escalating the problem back to Bungie, they pointed out the problem. My computer didn't manage to reach their CDN, so the game got angry and spat the Nightingale on my face. They also hinted me about what my computer did instead and ...
Somewhere in the guts of the Destiny 2, there is a component reading the value of environment variable HTTP_PROXY. I had that set on the PC because of ... something I did for software development years ago.
After deleting the variable, the game started. WHOA!
So, it wasn't my router, DNS, firewall, or ... whatever I attempted before. Problem solved!
In general the Nightingale-error is a generic catch-all networking failure. So, _something_ in your networking isn't working as the authors of the game expect. Most often I bumped into DNS-issues. As any regular-Joe is using their ISPs DNS for requests, they might cache your query results too long making your game attempting to connect to a server which doesn't exist anymore.
Other than that, with the initial information you offered, I don't think I cannot assist you more.
According to Bungie support, in Destiny 2 Nightingale is a code for an unspecified network error. That would include you not paying your Internet bill, unplugging the cord on your router or failure to resolve a DNS-record.
Whatever the reson would be, Destiny 2 cannot talk to Bungie servers spitting a Nightingale on you.
To track down exactly what's wrong with your setup is impossible. With a 60% probability it has something to do with your router and 35% probability something to do with your computer setup. Btw. Nightingale error does exist in X-box and Playstation versions too.
Given that, it is impossible to solve every possible permutation of a failure. I described what my problem was and how I fixed it.