Posted this issue on my own thread earlier but then talked about it more on the Discord server where I was asked to bring it here.
To be as detailed as possible: I can no longer access Grand Dream City or the Tournament Stadium, nor can I continue the story as a result. I had defeated Adam in the tournament and the cutscene with Bladestar's attack played out. Rhodea called for me and the others to meet with her in the purple-ish structure to the left of the stadium entrance. From what I've seen on YT, this is when she briefs you and the others on the situation and what to do next. I haven't paid too much attention to avoid spoilers.
However, none of this happened for me because after Rhodea and the others left, I went elsewhere to do sidequests and capture some pokemon. After quite a bit of progress I returned to the train station in route 9 to return to the stadium, and I was unabled to. The stadium was no longer listed as an option as seen in the screenshot below, and at this point in the story, GDC is completely locked down and I have no means of accessing it via fly, ground, or train. Police block all entrances in the Terrial Region as well as the train station in West Gearen. I even tried using both doors on the route 9 train to see if that would make a difference, but it didn't. Selecting Route 9 from the options just (predictably) brings me right back to where I was standing with no other new options presenting themselves.
After all we've been through, the deaths, backstabs, life threatening dangers, giant pokemon, and a maid cafe, all my friends are waiting for me and I'm stopped by a bus.