Curious at ATC @ KMIA

So there was this tower controller @KMIA who cleared landing as 1 for me @rwy 08R when suddenly i saw an aircraft on the rwy so i cancelled my landing and contacted tower for a go around but his response was “please follow instructions” i am not sure why? and he instructed me to see the manual for using atc instructions. i was very close to landing :| any guesses ?

Firstly, TS1 or expert?

Secondly, did you line up with wrong runway? Very common mistake at KMIA

EDIT: Controller confirmed it was that ↑, see below. Also confirmed to be on expert

If this is recent and on the Expert Server, DM your controller. Tower controller at the time was @Matt_McDonald

Yes. He lined up on the wrong runway.