Gallen has not fought since his unanimous decision victory over Puna Rasaubale in 2017.
The former Sharks captain recently knocked back a chance to fight Hopoate in November, after committing to a rehabilitation program with the Sharks for a shoulder injury he carried through the end of the 2018 NRL season.
Gallen's ducking saw Hopoate come out and publicly slam the former NSW State of Origin captain.
Hopoate told The Sunday Telegraph last month Gallen is a "coward".
"He talks up a big show, he accepted the fight and now they're telling me he won't sign the contract," Hopoate said.
'Either sign the contract or retire from boxing.
"He knows what's happening if he jumps in the ring with me, that he's getting knocked out, and that's why he's running scared and won't sign."
Hopoate was recently spotted re-enacting his infamous "Hoppa" incident when he finger-poked opponents at the Legends of League tournament on the Central Coast last month.
Wearing a white glove, Hopoate appeared to focus on the nether regions of several Newcastle Knights legends during the exhibition event.