Does anyone remember a cartoon show from probably somewhere in 2000 to 2015? It involved magic cubes, a yellow robot sidekick, a big Mexican mechanic, and a girl who couldn't sing.
Di-Gata Defenders (2007).
The series follows the travels and adventures of six teenage children, part of an organization called the Di-Gata Defenders. Their mission as heroes is to defend the planet Ra Dos against evil factions. Seth, Melosa, Erik, Kara, Rion and a Sixth Ranger must defeat the evil Lord Nazmul and his Order of Infinis before they take over Ra Dos. The team meet many friends and allies along the way but also encounter enemies. Knowing just who is friend or foe is vital if the Defenders are to succeed in their mission.
Also from the same page:
Dreadful Musician: Mel loves music, but she's a terrible singer.
The opening has the summoning cubes and the yellow robot:
Remembered from my own answer to Show like Pokémon, but with dice that have runes.