well, basically you want to infer n = x_train.shape[1] number of parameters from 1 observation - you are not going to have enough information from the data and the posterior you get will most likely be dominated by the prior.
Moreover, since you don’t have the data on which specific individual had left the company, all the information will just “flow” back to the intercept (as that’s the common factor shared across) - it is thus impossible to estimate the coefficient accurately.