Catfights and Spotlights debuted at number eight in the album chart last month and has since dropped out of the top 40.
"The sales have been disappointing but I don't think it is a reflection on the album's quality," Range told the Daily Star Sunday. "The problem is the promotion, I don't actually think our fans know we've even got an album out."
The band's long-time rivals Girls Aloud debuted at the top of the album chart with their latest offering Out of Control earlier this month.
Keisha Buchanan added: "Of course we would have loved ours to go to number one but we still sent flowers to congratulate the girls. We're not going to lose any sleep over it and will be back in the lab soon to start again."
> Click here to read our review of Catfights and Spotlights