d.rickman gave me the best hint and requested I post:
My cutting mat was warped by an iron.. yes, i used it to iron .. a brief mistake.. the mat warped.
d.rickman put her own warped Cutting mat outside in the HOT sun for several hours, let it cool completely for several more hours and ... It worked ! Flattened out !
Great hint ! Waiting for one of those last 90 degree days that sneaks up on us this late.
Thanks for the tip !