\cmidrule not working on second column

Question

I have been trying to get a line under the first cell of the second row but instead the command is working on the first row. While it is working on the others.

my code:

\documentclass[conference]{IEEEtran}
\usepackage{cite}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{algorithmic}
\usepackage{graphicx}
\usepackage{textcomp}
\usepackage{tabularx,booktabs,ragged2e,bm,newtxmath} % new packages
\usepackage{pgfplots}\pgfplotsset{compat=1.16}
\newcolumntype{Y}{>{\centering\arraybackslash}X}
\usepackage{xcolor}
\def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em
T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}

\begin{document}

\begin{table*}
\setlength\tabcolsep{3pt}
\caption{System variables dependencies}\label{tab2}
\begin{tabularx}{\linewidth}{@{} X *{5}{Y} @{}}
\toprule
System variables 
& $o_{v}$
& $s_{p}$
& $t_{m}$
& $l_{ft}$
& $l_{ot}$
\cmidrule(l){2-2} \cmidrule(l){3-3} \cmidrule(l){4-4} 
\cmidrule(l){5-5} \cmidrule(l){6-6}
\addlinespace
Subsystem associated & V & Pr & M & $\textrm{T}_\textrm{1}$ & 
$\textrm{T}_  \textrm{2}$ \\
\addlinespace
Mathematical dependencies & & & $t_{m}(t)=23-0.25
\times  o_{v}(t)+0.62\times s_{p}(t)$
& $l_{ft}(t)=l_{ft}(t-1) -0.001\times s_{p}(t)$
& $l_{ft}(t)=l_{ft}(t-1) -0.0005\times s_{p}(t)$ \\
\addlinespace
Operational dependencies & $o_{v}(t)=0$ if $s_{p}(t)=0$ & & 
& $l_{ft}(t)=l_{ft}(t-1)$ if $s_{p}(t)=0$
& $l_{ot}(t)=l_{ot}(t-1)$ if $s_{p}(t)=0$ \\
\addlinespace
Nominal value range 
& $0\rightarrow100$ (\%) 
& $0\rightarrow100$ (\%)
& $23\rightarrow83$ (°C)
& $2\rightarrow100$ (\%)
& $2\rightarrow100$ (\%)\\ 
\bottomrule
\end{tabularx}
\end{table*}
\end{document}

Answer 1

Give \\ before \cmidrule

\documentclass{book}
\usepackage{cite}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{algorithmic}
\usepackage{graphicx}
\usepackage{textcomp}
\usepackage{tabularx,booktabs,ragged2e,bm,newtxmath} % new packages
\usepackage{pgfplots}\pgfplotsset{compat=1.14}
\newcolumntype{Y}{>{\centering\arraybackslash}X}
\usepackage{xcolor}
%%%% remove this line and the two below (here just commented)
%\def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em
%T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}

\begin{document}

\begin{table*}
\caption{System variables dependencies}\label{tab2}
\begin{tabularx}{\linewidth}{@{} X *{5}{Y} @{}}
\toprule
System variables & $o_{v}$ & $s_{p}$ & $t_{m}$ & $l_{ft}$ & $l_{ot}$\\
\cmidrule(l){2-2} \cmidrule(l){3-3} \cmidrule(l){4-4} 
\cmidrule(l){5-5} \cmidrule(l){6-6}
\addlinespace
Subsystem associated & V & Pr & M & $\textrm{T}_\textrm{1}$ & 
$\textrm{T}_  \textrm{2}$ \\
\addlinespace
Mathematical dependencies & & & $t_{m}(t)=23-0.25
\times  o_{v}(t)+0.62\times s_{p}(t)$
& $l_{ft}(t)=l_{ft}(t-1) -0.001\times s_{p}(t)$
& $l_{ft}(t)=l_{ft}(t-1) -0.0005\times s_{p}(t)$ \\
\addlinespace
Operational dependencies & $o_{v}(t)=0$ if $s_{p}(t)=0$ & & 
& $l_{ft}(t)=l_{ft}(t-1)$ if $s_{p}(t)=0$
& $l_{ot}(t)=l_{ot}(t-1)$ if $s_{p}(t)=0$ \\
\addlinespace
Nominal value range 
& $0\rightarrow100$ (\%) 
& $0\rightarrow100$ (\%)
& $23\rightarrow83$ (°C)
& $2\rightarrow100$ (\%)
& $2\rightarrow100$ (\%)\\ 
\bottomrule
\end{tabularx}
\end{table*}
\end{document}

PS: I didn't check your code except the error