Checking for enchantments tag

i have a really simple execute command in my function that checks for a shield in your off hand with my custom enchantment, however it seems to only work if i dont check for the enchantment, does anyone know how i can fix this?
execute as @s if entity @s[nbt={equipment:{offhand:{id:"minecraft:shield",count:1,tag:{Enchantments:[{id:"medievalweapons:absorption"}]}}}}] run effect give @s instant_health 1 1 true