Minecraft wiki entry for scoreboard, associated text: Syntax
scoreboard players enable <targets> <objective> (Java Edition)
Description
Enables the target(s) to use the /trigger command on the specified objective. This command accepts non-player entities, but only players are able to actually use the /trigger command. Until this commnand has been run, players can't /trigger that objective. Using the /trigger command will disable it again.
Note that if the targets did not previously have a score for that scoreboard, this command will set the its score to 0.
Arguments
<targets>: score_holder
Specifies the score holders.
Must be a selection of score holders. It may be either a target selector, a player name, a UUID, or * for all score holders tracked by the scoreboard. Named player needn't be online, and it even needn't be a real player's name.
<objective>: objective
Specifies the objective.
It must be an valid scoreboard objective name.
Result
Command Trigger Java Edition
... enable ... the arguments are not specified correctly Unparseable
<targets> fails to resolve to one or more score holders Failed
the objective doesn't exist
the objective's criterion is not "trigger"
all the targets' scores are already enabled
On success Enable the trriger command on the objective.
Output
Command Edition Situation Success Count /execute store success ... /execute store result ...
... enable ... Java Edition On fail 0 0 0
On success 1 1 the number of the targets whose scores are newly enabled