lavaan ERROR: initial model-implied matrix (Sigma) is not positive definite;

[pdldeepen]

I am to make MIMIC model. When I model with raw data then the model runs but when i make the variables stationary the model shows error. How do I solve this problem and make a MIMIC model
diff = read_xlsx("C:/Users/Deepen/Documents/R/diffdata.xlsx")
diff.cov = as.matrix(diff, rownames = 1)

model = '
se =~ gdppc + ur + rl + cc + gs + dt + ndt
cic ~ se
lfp ~ se
cg ~ se
'
unfit = sem(unmodel, data = diff.cov)