On
On[symbol::tag] switches on a message so that it can be printed (reverses Off).
Examples
Re-enable a message:
Off[General::spell1]
(* ... later ... *)
On[General::spell1]Enable tracing:
On[f]
(* Trace evaluations of f *)Enable multiple messages:
On[Power::infy, General::argx]Please visit the official Wolfram Language Reference for more details.