You are mistakenly pointing to the data table handle when referencing the report output. Report output is the result of a JMP Platform. I suggest you place your output into a Border Box() and then save it to HTML.
See
Help==>Scripting Index
for what objects can be issued the << Save HTML message
dt= Open( "****.xlsx" );
New Window("mt report",
nwBB = Border box(
V List Box(
Graph Builder(.....);
Graph Builder(.....);
)
)
);
nwBB << Save Interactive HTML("C:\Users\123\Desktop\Test.html");
;
Jim