John Still had been keen on signing Miller on a permanent basis, and he could have left Priestfield on a free transfer, but the League Two side were unable to afford his wages.
Manager Mark Stimson has now revealed the Gills had offered the 27-year-old the opportunity to leave the League One club, but that deal was turned down.
Stimson told the Kent Messenger: "Adam and his people have refused the agreement we've offered. With Adam, that's it. It's done."
Source: Team Talk
Source: Team Talk