I can only make an educated guess, but judging by the length of the song being approximately 2 minutes and having a lot of things in it and stuff, I'm going to assume it's because DefleMask tries to export a file that goes over the amount of RAM the C64 can handle. DefleMask exports are, afaik, just massive register dumps, and take up a lot of space. I have observed that a track in DefleMask around 1 minute in length with a lot of arpeggios and embellishments usually takes up around 32kb, which is half of the machine's total RAM of 64kb.
With your tune being slightly over 2 minutes long, and it having a lot of effects and modulations and things, it most likely exceeds the amount of RAM the C64 gives its user, and wouldn't ever possibly play on the machine.
All I can really do is to suggest switching to a different editor for Commodore 64 music, such as GoatTracker, CheeseCutter, SID-Wizard, or some other tool, as DefleMask is quite possibly the worst tool you could use to make music for the machine.
With that said, the track itself isn't bad at all.