Is there an error in your " To access the responsive themes in Zoho Sites, go to Themes > Gallery and click on Responsive from the category list on the left-hand side."

i emailed the same question, but posting here for a faster reply

Went to https://www.zoho.com/sites/theme.html

There is no ‘gallery’ listed.  I think u mean [to look at] the listing on left that says

Art

Beauty

Business

Constr

Ect  

‘responsive’ is not listed there

i am very happy that u added the responsive templates . thanks leonard