Hello Lisa and welcome to Beoworld,
Any CD-R should work with a Beocenter 9000. If you have burnt a CD-R and it won't play then the issue is in the Beocenter. The CD mechanism needs new capacitors. I have two BC9000s and they both needed new capacitors before they would play CD-Rs. I am fairly sure that CD-RWs will never work in a BC9000.
Richard
Some of my B&O: BV3/32, MX7000, MX5500, LX5500, MX4000, BM8000, BM6000, Overture, BL8000, BM6000 Quad, BM4400, BM3400, BG-CDX, BM3000, BM1001, BM1200, BM1600, BM1700, BM1500, BM1400, BM2400, BM2300, BM4500, BM4000, BVM70, BVS45-2, BVS60, BC7700, BM2200, BM1900, BG8002, BM1202, BVPenta, BVP45