Plsfold, did you get liquid with your order?
You need to make sure the atomizer is wet at all times, more so with a 510. Put a drop or two on the atomizer bridge each time you refill your cartridge. Refill often, especially if the flavor changes. If you vape them dry, for too long the wicking under the bridge gets singed, and a bad flavor develops on the 510.
The plastic flavor could be the liquid in the cartridges (some China liquids have a perfumy/plastic taste).
On occassion, the center bridge can be off center, and if you are huffing your new toy

, it can melt the cartridge a bit. Check to see if it is centered or if your cartridge shows any sign of melting. If so, use something small to very gently move it to the center of the atomizer. Doesn't happen often, but will give a nasty taste.
Joye attys don't have a bad primer flavor to them (it is just PG). So don't worry about "primer" as the problem (trust me, I've gotten over 50 new 510 attys in the last few months... I never get a bad flavor out of any of them). Just keep that atty wet!