The default theme used for my web site stopped loading all of sudden.
I got the following error message:
"An unexpected error occurred.
Theme not found in /hermes/web08/b2756/pow.williamliu/htdocs/hymarkint/c5/concrete/config/../themes/greek_yogurt"
Then, I went to check with my hosting server if the theme files still exist. They do!

I suspect that it is concrete5 problem. Does anyone have any idea on how to correct this issue?
Thank you so much.

Regards,
William