Hi everyone. Does anyone know how to post after seeing an error page?

https://bigclosetr.us/topshelf/node/add/fiction
Error
The website encountered an unexpected error. Please try again later.

I have not been able to add a single new chapter to this site and i have been trying to for the last week. I know it's not a wide problem as there have been entries submitted within the last few hours (at the time of this upload). I have tried on my phone (my usual method) and my computer. I get the same message. Can anyone help me?