Error: 'makevars_user' is not an exported object from 'namespace:withr'

i'm bit new to R and facing some issues while getting the CLV by following the below link

I'm getting below error
Error: 'makevars_user' is not an exported object from 'namespace:withr'

while fitting the model
model_fit <- stan(file = "full_clv.stan",
data = model_data,
chains = 4,
iter = 1000)

I'm using R Version-3.6.1 and Rstudio Version 1.3.1056

Any help would be very helpful. Please let me know in case any more details are required from my end.

Didn't realized that withr is implicitly called from rstan, removing rstan and withr and then installing them back in reverse sequence fix the issue.