Sweating on the outside of an already COLD and charged up tank is NOT good. However, if this tank had sat for a little while and was fully room temp thru-out -- it may not be a sign that something is wrong. As it cools down, it will by nature atract the condensation of any humidty in the air.
The proper way to charge these is to slowly fill them, say about 1/2 or so, then let it soak into the internal insulation to hold the charge. Repeat again - and it will take less to get liquid visible. Once full -- let sit over night. The "Regulations" the shipping comapanies follow is that NO LIQUID be present. I don't agree with that at all. The local bull stud ALWAYS sends thier out with at least a 1/3 liquid volume, and that is after a full overnight charge.
It might just be that it got fully warmed up and will take a little time to recharge before it quits sweating. If you find that it has frosted over -- all around - during the night, then I'd say for certain it has gone south! Maybe even NORTH in your case -- hehehe!
Patience may be the key here -- A couple gallons or so of Ln2 is a fairly cheap testing method! If in doubt though, just send it back empty and have them test it -- might be the best for every one!
Good luck -- Terry