So, just throwing this out there in case someone else runs into the same bug. It’s a bad one (complete showstopper with no fix ETA) and judging by the Google results, not exactly rare.
Once you’ve completed the missions to upgrade the Base of Operations (typically concluding at the Federal Emergency Bunker if you go by levels), you get a mission “Reactivate the SHD Network”. This involves going into the basement of the White House to interact with a server down there, at which point you get a brief cutscene.
Well, this mission bugs out. A lot. I have my theory that it involves doing the Federal Emergency Bunker in a group, then someone in that group turns in the mission while others are not in the White House. That’s what happened to my friend, unfortunately. I had turned in the mission, he was still on the outskirts of the Federal Emergency Bunker sorting through loot and didn’t get mission credit. He would get prompted to restore the network himself, but the server you’re supposed to interact with he couldn’t do anything with. No interact prompt.
If you find yourself in this situation, you’re unable to get credit for the final stronghold (Capitol building). You can tag along in a mission with a group, but you’ll be flagged as ineligible because you’ve yet to complete the main quests (the Restore the SHD network) and won’t receive credit. This also means that you’ll never be able to progress to WT1 and beyond or pick a specialization.
Your only hope is by waiting for ages at the Federal Emergency Bunker and hope you can matchmake into someone running the mission that hasn’t completed it yet. You then have to hope that said person fast travels to the White House, goes into the server room, and interacts with the server. That’s the only way out for now. Unfortunately, that mission is flooded by L30’s trying to do the same thing, so matchmaking into a “clean” mission isn’t likely.
I ended up spending Sunday leveling up a new character just to be able to run that mission for my friend and got him unstuck that way, but what a nasty bug. It’s a little upsetting that this was reported in Early Access, acknowledge by Ubisoft as a bug that they are investigating, but still not hotfixed. It really is a total showstopper and it’s super frustrating that the thing that invalidated your L30 character was the inability to watch a pointless cutscene.