Minecraft add player to team based on scoreboard score
The command for adding players to teams is:
scoreboard teams join [teamname] [players]
And the code that means "all players" is @a
That means, to add everyone to a team we do
scoreboard teams join <teamname> @a
All we need to do is add a modifier to @a to accomplish what you want You had it right, but you were saying when there score is a maximum of one. This is the command you would use:
scoreboard teams join Rank1 @a[score_ranklvl_min=1, score_ranklvl=1]