Why does my extra-firm mattress feel soft or sunken in the middle?

A center dip on a foam bed almost always traces to its support surface, not the foam itself. If this mattress sits on a slatted base with wide gaps, a flexing box spring, or an unsupported center rail, the foam sinks where it lacks backing. Set it on a solid platform or a foundation with slats under 3 inches apart and a supported center. The 5-year warranty excludes sag caused by an inadequate base, so proper support matters.