If you have downloaded all of the RealTracks and RealDrums, then I agree that it might be a paths problem.

Check that these locations are correct from Options > Preferences:

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BIAB & RB2026 Win.(Audiophile), Windows 10 Pro & Windows 11, Cakewalk Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Session Keys Grand S & Electric R, Kontakt, Focusrite 18i20, KetronSD2, NS40M, Pioneer Active Monitors.