I've been having the same issue since last year. My work around was purchasing the game for my ps4 to get loaded so i can eventually log back in on my PC. Unfortunately after i completed a Duty, i can't log in at all with this same error described above. I've tried every recommended fix outside uninstalling and reinstalling. I even installed a new video card but still cant log in. Just stays stuck on the loading screen.
SO basically its like this. I completed a duty on the PC and exited the instance. It stood loading for over 5 minutes with the chat channel still active. I forced the game to close and restarted. I selected my character who completed the duty on the ship in the StormBlood expansion and the screen went to the loading screen. It then makes a sound similar to a ring being collected in Sonic the hedgehog, but remains loading no matter how long i wait. I log into the PS4 version, played a bit til i got to the Ruby sea to negotiate the Fee to cross the sea. I tried to log into the character on the PC, who is at the Ruby sea but am unable to. It just stuck on the loading screen. I can log into another character just fine who is currently in ARR.
With DX11 on, I get no error codes. When i changed to have it off, I finally got an error code (after many many attempts to log in):
ntdll.dll+5E1A9
AcLayers.DLL+2C555
ffxiv.exe+1001677
ffxiv.exe+FE4b54
ffxiv.exe+5BEAB
ffxiv.exe+5AB22
ffxiv.exe+59374
ffxiv.exe+3C30CB
I am not sure if it related to me not being able to log in with that character on my PC, but its finally an error code.
I am running Win 10 Home 64bit, 16 gb ram, DirectX 12 installed, AMD Radeon R7 360 series and it is the Steam version.
Edit: Logged into the ps 4 version and teleported to New Gridania. I then logged into the PC version and was able to get in with no problem. I then teleported back to Ruby sea and it crashed. I got an error code but it went too fast and was able to read or get a print screen. Will try to get those error codes at another time.