Advanced bed antec

Ever tried one of those euro sealers? - euro sealer

I bought one the other day because I thought it was candy for sealing bags of them in good Xmas .. but he used to work the damn thing! What am I doing wrong? I pressed for 3 seconds or more .. and slide down ... and anything with blood. I even put new batteries new and different in. .. blah! Shall I continue where I am and try to change that? or function of these things really are.