The Code I ran:
\begin{table*}[htbp]
\caption{alekga g. The number of stars represents the strength levels. (* = good, * = better, * = best)}
\centering
\begin{tabularx}{\textwidth}{|>{\centering\hsize=0.3\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.05\hsize\arraybackslash}X|>{\centering\hsize=0.35\hsize\arraybackslash}X|}
\hline
&
\multicolumn{7}{c|}{\textbf{Strengths}} &
\\ \cline{2-8}
\multirow{-2}{*}{\textbf{Techniques}} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{Complexity }} \end{turn} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{Accuracy}} \end{turn} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{Robustness }} \end{turn} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{VSTLF}} \end{turn} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{STLF}} \end{turn} & \begin{turn}{90}
\multicolumn{1}{l}{\textbf{MTLF}} \end{turn}& \begin{turn}{90}
\multicolumn{1}{l}{\textbf{LTLF}} \end{turn} &
\multirow{-2}{*}{\textbf{References}} \\ \hline
LSTM &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{X} &
X &
\cite{Rafi2021,Phyo2019221,dat_hybrid_2021,YANG2022108150,Han2019,Fang2022,JAVED2022117689,JHA2021107479,SHI1,GUO20201046,Xuan2021} \\ \hline
SVR &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{*} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{***} &
*** &
\cite{KAVOUSIFARD20146047,WANG201265,en5114430,en9020070,FattaheianDehkordi2014,Tran20223410,KONG2020114368,Niu_2021,ZHANG2012850,KAYTEZ2015431,Alire2019,Li2016,Zhang2020,Zeng2018,en9100827,Jawad2020} \\ \hline
ANN &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{***} &
*** &
\cite{Mohammed2022,article11,Hamzacebi2019,OFORINTOWJNR2021102679,su14010188,rizk2020,WU2013126,arssfdticle,Kavousi-Fard2014517,golilarz_short-term_2021,Farfar2019,Phyo2021,kuruge,Gafar2018,essallah_comparative_2019,YU2015176,ARDAKANI2014452,AZADEH2013605,GUO20181186,Cheng2020,salgado_hybrid_2013,Liu2021,Gao2020,MOAZZAMI2013489,Ma2020,articsdale,YU2014102,BENDAOUD2021111152,en12122445,sarvba,en14175510,Sheikhan2012,azadeh_optimization_2014,houimli_short-term_2020,hu020,Mir2021,liu_short-term_2021,ARVV3,electronics11101524,Ananthu2021114,Bedi2018} \\ \hline
Time series &
\multicolumn{1}{l|}{*} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{*} &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{**} &
*** &
\cite{saleh_hybrid_2014,KAZEMZADEH2020117948,fard201223,VELASQUEZ2022123483,paperi021,Xie2017,LEE2012251,HAMZACEBI2014165,zeng2017,YUKSELTAN2020100524,en13205309,ZHAO2016272,paul2019,Han2021,Li2018,CHRENG202276,SERRANOGUERRERO2021117173,migon2013,9403196} \\ \hline
ANFIS &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{**} &
\multicolumn{1}{l|}{*} &
\multicolumn{1}{l|}{***} &
\multicolumn{1}{l|}{X} &
** &
\cite{SHAO2015876,Fallahpour2021142,mollaiy-berneti_optimal_2016,jain2019,PatiRaySingh+2022+59+72,LAOUAFI2016136,Cevik2015,artitiancle,rahtor20} \\ \hline
\end{tabularx}
\label{st4}
\end{table*}
The error i got:
\multispan ->\omit
\@multispan
l.818 \end{tabularx}
I expect to see \omit only after tab marks or the \cr of
an alignment. Proceed, and I'll ignore this case.