Does the wire burn back into the torch and then drop off onto your base metal? If that is the case then I ask this...
Is the liner shot or kinked? It sounds like the wire isn't being fed fast enough. Check the wire feed rollers, cable liner, electrode, (make sure it is the right size and not excessivily loose),and reel tension. Check to see that the wire unwinds smoothly from the roll and isn't all tangled up. (they call that "birdcaging".
You should be able to release tension from the drive roller and draw the wire through the cablehose from the torch end with relative ease.
If you can't pull it through by hand then check the things I mentioned.
Also, you would do well to get a new roll of wire. .023 or.030 er70s6 is good general purpose wire.
Was the unit set up for gas when you bought it? I wonder if there is some flux core wire in it? It should weld ok with gas unless you switched the polarity. (should be ground positive for gas welding)
Does the wire hit the base metal and then melt without penetration? I'd guess that then the polarity is reversed or your wire speed is too high.
Play around some..Set the heat setting all the way up and bring the wire speed up till it welds. Use a piece of 3/16 so you aren't bothered by burning through. If you cant get it to weld after all of that then you might have issues with the circuit board or a diode.
Hope this helps,
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