Yep; turning off adblock fixed it.
Some NSF errors:
oh boy... there's a load of confusion here. I'll do my best explain it.
This game is actually Yume Koju Doki Doki Panic, the game before it was turned into Super Mario Bros. 2 and should be switched with and renamed to Super Mario Bros. 2 The Lost Levels and here is the NSF for it.
I have tested Super Mario Bros. The lost Levels on my FDS and there is extra audio, but there is no official game called Super Mario VS for the Famicom Disk System, instead it was an arcade game that someone ported to iNES; hence you need to adjust the right pallet for it.