First, if we translate the entire meaning naturally,
→ “If you already bought a ticket, leave a comment below!”
if you coped
cop = (slang) to buy, to get hold of
Originally it meant “to catch,” but in hip-hop and street culture,
It has solidified into the nuance of “successfully bought/got what I got.”
copped is past tense → “if you already bought it”
your tix
tix = abbreviation for tickets
Very common in text messages and social media.
Not used in official documents, only used when talking to fans