Filming for the VH1 reality series' latest installment was originally scheduled to begin on Tuesday, however that plan has been scrapped because producers are having a hard time completing the celebrity cast, TMZ reported.
Former A Shot at Love star Tila Tequila had committed to be a Celebrity Rehab cast member early last week, while former Laguna Beach star Jason Wahler was also reportedly "very close" to an agreement to appear on it.
In addition, Bone Thugs-N-Harmony rapper Bizzy Bone -- whose real name is Byron McCane -- expressed interest in participating in the VH1 reality series to receive treatment for marijuana and alcohol addiction.
However there were still "holes in the roster," according to TMZ, which reported that the series' fourth season is still lacking a headlining star for its cast.
While sources told TMZ that producers offered troubled actress Lindsay Lohan $1 million and her own show if she would appear, she turned it down.