Lavaan error: Multigroup multilevel mediation analysis

[Yingjie Yuan]

Hello everyone, 

I got an error message when modeling a multilevel mediation model (a 2-2-1 model, with 900 cases at level 1 and 300 units at level 2) across three groups (repeated measure, each unit is in three groups). 

The syntax is as follow:

multigroup.model<-' 

group: low   

level:1

DV~1

level:2

DV~b*IV+c*Med

IV~a*Med

group: moderate   

level:1

DV~1

level:2

DV~b*IV+c*Med

IV~a*Med

group: high

level:1

DV~1

level:2

DV~b*IV+c*Med

IV~a*Med

#indirect and total effects

ab:=a*b

total:=ab+c'

multigroup1<-sem(multigroup.model, data=df,cluster="RankID", group = "g", 

                 fixed.x = FALSE,std.lv = TRUE, h1 = TRUE)

Then I got this error message: "Error in if (fx.delta < tol) { : missing value where TRUE/FALSE needed". 

Can anyone help check if this syntax is correct? My aim is to test and compare this 2-2-1 multilevel mediation model across three conditions of the group variable (high, moderate, low). 

Also, can anyone advise how to solve this error?

Thanks a lot!

Yingjie