Thanks for the comment, I noticed that most of the test cases I had issues with, actually had the 'Expected' and the 'But was' values turned around. So rather than me thinking it wants the output "0:0:0" that was my actual output with one of the test cases and not "00:00:00".

I wrote this in Python and works perfect. When you reduce secs to mins then to hrs, they firm integers that computer displays single digit when less that 10. So it needs to be converted into string and concatenate '0' (note: it's not an integer). Hope it helps,

All tests pass, displays "00:00:00" format perfectly, thanks

Same issue as DisturbedNeo:

Expected: "0:0:0"
But was: "00:00:00"

I even configured my coding so it should display "0:0:0" at certain scenarios, still did not work.