This message seems to indicate that you have one or more variables in your data set on which all cases are missing (or, in other words, on which there are no valid scores for any individual). Could that be true for one or more variables? If so, that variable (or those variables) could not be used in your analysis/model because there has to be at least some information (obviously) on each variable.

Otherwise, this message may indicate that Mplus isn't reading your data file correctly. Have you checked the data file and VARIABLE command for any potential errors (e.g., incorrect NAMES list)?

Thank you for your response! I checked, and there are not any variables in my data set on which all cases are missing.

I converted Spss file into dat data file using the save as option. And I copy pasted the names of the variables from the Spss data. I can not understand why Mplus isn't reading it. I attached my input to this response. Is there something I did wrong?

It is impossible to know what went wrong by just looking at the input file (syntax). You need to check your data file (exp.dat) to see whether the columns/entries in that data file match with what you have in your NAMES list in the VARIABLE command. I'm almost certain that there must be some sort of mismatch between what's in the exp.dat file and the variable names list in your input file.

You can also try using a reduced set of variables (using the USEVARIABLES option) and requesting ANALYSIS: TYPE = BASIC; to check the descriptive statistics for that reduced set of variables to see if that works. That might bring you closer to identifying the problem.