Complex sentence: At the end they chose to work with Erwin and booked the studio for October 15, but they weren't prepared recording because they didn't have a bass player and none of the auditioned bass player didn't have availability to the demos recorded by the band.
Split into simpler sentences: At the end they chose to work with Erwin and booked the studio for October 15. However, they were not prepared for recording because they did not have a bass player, and none of the auditioned bass player had had access to the demos recorded by the band.