SummaryFilletSrf is limited to handling exactly three surfaces that meet at a point. Here's a technique that will work if you have 5 surfaces to fillet.

Five surfaces

Download Rhino 3DM file

Original polysurface with 5 planar surfaces meeting at a single point.

Use FilletSrf with Extend = no and Trim = no, to fillet all adjacent surfaces, and opposing surface combinations, except the two that are the farthest apart.

Split the combinations of three fillet surfaces by isocurve where their exterior edges intersect.

Delete the extra parts of the fillet surfaces, leaving just the portions needed.

Draw three spheres so their centers are in the center of the arcs that define the bend boundaries.

Trim away the portions of the spheres that are not needed using the surface edge curves with the CRV sub-object picking option. Optionally Shrink the trimmed surfaces.

Trim the extended surfaces with the bottom plane, and the plane with the trimmed extended surfaces.

Extend the side fillet surfaces so they extend past the bottom planar surface.

At this point you can trim the original surfaces to match the filleted edges, or just make new surfaces from the surrounding planar curves. An easy way to do that is join all of the fillet surfaces and sphere fragments, and Cap the planar holes.