I had the very same problem but through a lot of frustration I was able to solve the problem. Don’t know if it will do the trick for everyone else but it worked for me.
After I created my blog I set up a desktop icon so that I could easily get to my blog administrator for creating posts. Apparently when setting up the desktop icon something got lost. It got me to my wp-admin ok so that I could login with my id/password and I was able to see everything as normal except when I went to make a post. I had ‘Error on Page’ and it wouldn’t allow me to type anything in the edit area.
But …if I bypassed using the desktop icon and simply used internet explorer and typed in:
https://www.sitename.com/blog/wp-admin
the problem went away.
Looks like something got lost in setting up my desktop icon.
