We recently upgraded to Elixir 1.15 and noticed that certain errors like LiveView process crashes were no longer being sent to Rollbar despite having enable_crash_reports enabled. The problem appears to be related to the fact that Rollbax registers itself as a handler to the old :error_logger, while Elixir has been moving to :logger instead.
There's a little more background and discussion in this issue: elixir-lang/elixir#13030