Replacing lower duct hose

I put in the new hose, have all 10 screws back in place but the bottom floor cover won’t go on tight. What do I need to do?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0