Have you set the ppd-argument to TRUE? Except for Gaussian models, the “classical” ICC is not useful, and you should rather focus on a different way of variance decomposition (as stated here: Rstanarm: extracting variance components). This is what you get when ppd = TRUE, however, note that this “ICC” will probably differ notably from ICCs you get when you fit the same model in the frequentist framework.
Just a footnote: functions that are related to model quality or model performance from sjstats have been re-implemented in the performance-package (which is part of the new “easystats”-project).