I've ordered many times using the order form on GDG over the years. Lately, I've been buying directly from Michael via FB Messenger and PayPal when he posts things for sale in his FB group. He's always been very responsive, and my orders usually arrive within two weeks.
I did have one instance recently with a different seller. I made a single typo in the email address when I sent the PayPal payment. PayPal told me that I made payment, and when I showed the seller the receipt from PayPal (he said he didn't receive the payment), he showed me that I made a typo. Luckily the other person didn't claim payment so cancelling and resending to the correct person was an easy affair.
Regardless, Michael is a good and honest dude. Hopefully you can get this sorted quickly.