[Limdep Nlogit List] Models can not run

[Thao Thai]

Dear Nlogit users,

I have a DCE design with 6 attributes and the syntax of the MNL model is at
the bottom of this message.
I have run a number of models, of which I can not run some of them.

    CL model  Heteroscedastic MNL  ML  Generalised MNL
Attribute only  AIC  Can run  Status=1 with maxit=200 Can run  Can run
Attributes and a subset of 6 SDCs  AIC Can run  Status=1 with maxit=200 Can
run  Status=1 with maxit=200
Attributes and more than 6 covariates and interaction terms    Can run
 Status=1
with maxit=200 Status=1 with maxit=200 Status=1 with maxit=200
Notes: MX and GMX model: 50 Halton draws

When I run the *nested logit model*, only one structure (;tree=
In(H,C,P,I,G)],Out(N)) can run (STATUS=0)  while others do not converge
(STATUS=1) with the message "Fixed parameter ... is constrained to equal
the value or had a nonpositive st.error because of an earlier problem."

When I run the *latent class* with  2 classes, STATUS =1 with maxit =100.
When I tried the 3 class LC model, I got the message "Maximum of  100
iterations. Exit iterations with status=1
Error   1027: Models - estimated variance matrix of estimates is singular"

The syntax of MNL is below and it run fine
  Nlogit
;lhs = cho, cset, alti
;choices = H, C, P, I, G, N
;model:
U(H) = rl_h1    * RL_H1  + rl_h2  * RL_H2
     + fl_      * FL_H
     + cr_h1    * CR_H1  + cr_2  * CR_H2
     + lo_h1    * LO_H1
     + sa_      * SA_H
     /
U(C) = com
     + rl_c1    * RL_C1  + rl_c2  * RL_C2
     + fl_      * FL_C
     + cr_c1    * CR_C1  + cr_2  * CR_C2
     + lo_c1    * LO_C1  + lo_c2  * LO_C2
     + sa_      * SA_C/
U(P) = pri
     + rl_p1    * RL_P1
     + fl_      * FL_P
     + cr_p1    * CR_P1  + cr_2  * CR_P2
     + lo_p1    * LO_P1  + lo_p2  * LO_P2
     + sa_      * SA_P/
U(I) = ind
     + rl_i1    * RL_I1  + rl_i2  * RL_I2
     + fl_      * FL_I
     + cr_i1    * CR_I1
     + lo_i1    * LO_I1
     + sa_      * SA_I/
U(G) = gov
     + rl_g1    * RL_G1
     + fl_      * FL_G
     + cr_g1    * CR_G1
     + lo_g1    * LO_G1
     + sa_      * SA_G/
U(N) = non
     + rl_n1    * RL_N1
     + fl_      * FL_N
     + cr_n1    * CR_N1
     + lo_n1    * LO_N1  + lo_n2   * LO_N2
     + sa_      * SA_N
$
I am not sure what went wrong. I would be very grateful if you could
provide any insights on the problems that I am facing. Thank you so much in
advance.

Best regards,
T