ERROR: THE RAYLEIGH FREQUENCY 1.13523E-06 IS LESS THAN 0.00001 FOR LOAD. Someone who can help me with this, I am trying to design the foundation of this structure for which I use the reactions of the plate to transfer it to the staad foundation.

The superstructure is not connected to the mat as the base nodes of your superstructure are not part of the nodes that belong to the plate mesh. See screenshot below

If your intention is to take the reactions from the superstructure and design a mat foundation in STAAD Foundation Advanced, you may define FIXED supports at the column bases. take the reactions into SFA and create and design the mat in SFA itself