no complete element pairs

Hi I am trying to use the lavaan package for SEM,
after I enter my model specification,
I cannot do the model estimation by using the SEM fuction and R studio shows
Error in cov(data, use = "complete.obs") : no complete element pairs

The data set contains missing value but it did not happened when I did the analysis last night, and start to appear such warning after using another data set.

Please help! What should I do about it?

Model estimation <- sem(model1, data = rdata)

That's what I typed for model estimation