Error: could not find function "brm"

Code:
fit4 = brm(age ~ study_hours + (study_hours | grades),
data = set.date,
prior = NULL,
iter = 1000)

I get the error: could not find function "brm". brms successfully installed, don't have the slightest idea why it doesn't work. Can someone help, please?

Have you run library(brms) before you run the code you posted?
You only have to install brms once, but you need to run the library() function once for each R session.
An alternative is to name the package when you call the brm() function.

fit4 = brms::brm(age ~ study_hours + (study_hours | grades),
data = set.date,
prior = NULL,
iter = 1000)

Yup, totally forgot about that. I resumed this project so many times, I totally forgot. Thanks so much!