sed fails with “unknown option to `s'” error [closed]

I’m trying to use

sed -i -e "s/.*seb.*/    \"$ftp_login_template\"https://stackoverflow.com/" $ftp_dir

however I get this error:

sed: -e expression #1, char 34: unknown option to `s'

I don’t understand why since this works perfectly:

sed -i -e "s/.*wbspassword.*/    \"wbspassword\": \"$password\",/" $user_conf

Any ideas as to what I’m doing wrong?

Could this be the problem?
ftp_login_template=\${user}:${password}:24:86::\/var\/lib\/clit.${user}\/downloads:\/bin\/false\"