Can't log in to DMM Game Player. Anyone else having issues?

I have been playing the DMM version of the game for a few years through a VPN and haven't experienced any issues until today. Yesterday, before maintenance, I could launch the DMM player and play the game fine. Today, I can't get past the initial browser login screen of the DMM player.

I tried various japanese servers through NordVPN. I tried firefox and chrome. I ran DMM in administrator mode. I cleared my browser cache and cookies, I uninstalled/reinstalled DMM (v 5.4.22), restarted my PC. Tried different VPN protocols (UDP, TCP, NordLynx). No change.

This is what happens:

1. Set Nord VPN to a Japanese server (I cycled through most of them by now)
2. Launch the DMM player program
3. Click the orange 'browser login' button
4. log in to my DMM account in my web browser
5. get a login successful page on my web browser
6. nothing happens (normally it logs in automatically)
7. I also tried doing the browser login with DMM closed and then pressing the 'open dmm' button after the successful web login, but it just launches the DMM player app and asks me to do the browser login again.

Any advice on how to proceed? I've never had this issue before. Is there some sort of firewall setting? I don't see any rules in my windows firewall either way.