I have been having the same issue on my AC-5300 running latest stable FW: 384.14_2. It is stuck on updating, I have webui accessible via HTTP and HTTPS to no avail.
This is what I get in my system log:
Feb 8 13:50:06 kernel: [Sat Feb 8 13:50:05 EST 2020] Registering account
Feb 8 13:50:08...