Troubleshooting an error message "csvfiles does not contain any CSV files name"- rethinking::ulam()


I have been pondering about running a simple interaction between two categorical variables using rethinking::ulam() function for measuring weight changes between two treatments (treatment vs. control). Time points are recorded as factor type.

The fit function is quite simple using nlme package

lme(bmi~ trmt*time_pts+bmi_baseline,
                random = ~1|ID,
                na.action = na.omit)

Translating this simple linear mixed effect model to rethinking::ulam(), I wrote the following code:

dat<- list(
  P=case_when(df.long$time_pts ==1 ~1L,
              df.long$time_pts ==2 ~2L, 
              df.long$time_pts ==3 ~3L,),
  G= ifelse(df.long$trmt == 1, 1L, 2L)

fit.stan1<- ulam(
    B ~ normal(mu, sigma),
    mu <- a+ b[P,G]+ bm*bm +c[T],     
    a ~ dnorm(33, 5),
    sigma~ dexp(1),

    #adaptive prior
    matrix[P,G]:b ~ dnorm(0,sigma_a),
    c[IDf] ~ normal (bbar, sigma_bar),

    sigma_a ~ dexp(1),
    bbar ~ normal (0,5),
    sigma_bar ~ dexp(1)
  chains = 2,
  iter = 2000, 
  warmup = 1000

I believe I specified the model correctly, but it shows the following error message:

Warning: No chains finished successfully. Unable to retrieve the fit.Error in Stan::read_stan_csv(cmdstanfit$output_files()) : csvfiles does not contain any CSV file name

I am not sure what that error message is and how to trouble shoot it.
Any guidance on this matter would be greatly appreciated.

That means that there was an error in either the initialisation or estimation process - which could be an issue with either your data or your model. You’ll have to ask the ulam developers for guidance on how to get more information about the fitting/sampling if it isn’t being printed. Their github is here: GitHub - rmcelreath/rethinking: Statistical Rethinking course and book package

Thanks for your response!
Although I do not know exactly what happened, I was able to make the model run by replacing ID numbers (T=df.long$ID) to index ID ( T=1:nrow(df.long))). Leaving this message here just in case someone faces a similar problem and seeking STAN forum for a troubleshooting.