I have found ,I get to the log on page try to log on get the 504 page .Then if I go to another web page ie cyclechat then go back to mycyclelog it goes to the first page bypassing the log on page seems to work most times
Still down for me this morning. I think that may be that. Good while it lasted, especially as it was free, but understandable as it must have been an effort to maintain it. The owner had said they'd take it down some time ago IIRC.