Minecraft command gives an error?
Solution 1:
You have the OnGround portion inside the enchantment section which is inside the item section. You want it to be a part of the data tag but outside the item section. Also, you have OnGround value at b1 but that should be 1b. Similarly with the enchant values, they are missing s after id:0 and lvl:1.
Here is the corrected command:
/scoreboard players tag @e[type=Item] add example {Item:{id:"minecraft:leather_chestplate",tag:{ench:[{id:0s,lvl:1s}]}},OnGround:1b}