<cr> as a newline, you need to use commands which evaluate it as an expression. In this case, you need
:exe 'normal!' ")i\<cr>"
Or, as romainl says, you enter a literal newline using CtrlV Enter.
string string String expr-string E114
"string" string constant expr-quote
Note that double quotes are used.
A string constant accepts these special characters:
\... three-digit octal number (e.g., "\316")
\n newline <NL>
\r return <CR>
\<xxx> Special key named "xxx". e.g. "\<C-W>" for CTRL-W. This is for use
in mappings, the 0x80 byte is escaped. Don't use <Char-xxxx> to get a
utf-8 character, use \uxxxx as mentioned above.
:exe, you can also use
:exe 'normal!' ")i\r"