Problem with squeeks after installation of vinyl

I recently had Armstrong Cushionstep installed in my kitchen. The installer first pulled the indoor/outdoor carpet out that had been glued over composite/particle board (80's era) underlayment. I noticed after he took out the carpet that the composite/particle board underneath had been installed in three pieces, therefore we have three seams. Within a day or two after installation I started hearing squeeks when I walked over the seam areas of the flooring. The floor never made a squeek or sound before, only after the vinyl was installed, (and it was glued down). Was there an error in prep? He brought in a large loud sander to get the glue up before glueing the vinyl down. could the sander have loosened the underlayment? How can it be fixed to get rid of the squeeks? Opinions from the pros would be appreciated.