I did have a period in my FB advertising learning curve, when I tried to cheat with coupons several times. I created a new profile, added a coupon and PayPal email and submited an ad. I changed my primary PayPal email each time of course. It worked 4-5 times, then after a while I tried again and FB rejected my PayPal email, even if I added a new one to the same account.
I think the reason for this is that your PayPal account name and address doesn't change so eventually Facebook will blacklist your account name and every email you use with it.
It could be sooner, like in your case. Try to close PayPal account and open a new one. Even though your data will be the same, the account won't be.
Also, there really is no need to play with the coupons because you lose many data switching account like that. It's good to have all your ad performance data in one or 2 accounts so you can analyze it easier.