Recently my run, which was on leaderboard for almost year, was rejected and I dont understand the reason.

Those runs were missing the fading transition between two scenes when you hit 6 AM in the office. This gives a signficant advantage in time but isn't consistently replicable (at least at the moment), thus being pretty unfair to other players. I don't have the technical knowledge to explain why this happens but in case you encounter it again, restarting your PC will fix this issue the same way most problems are resolved when Windows is glitching out.