Welcome again, @pkon92.
It'll take some time. The buyer hasn't even had their 3 day option period yet!
Check this out, Shipping and read it thoroughly. You don't start calculating your payment days until the buyer has the item 3 complete days. The first time will always take a little longer as well. After that, it continues to speed up.
After your read all the shipping/payment info come back and let us know in about 7-10 days, how it's going.
I am having the same exact issue! It seems like OfferUp doesn't have their stuff in order. I wish I had known this sooner. I would have never made the deal. I am still waiting for my money as well! No way to contact support directly for a faster response. This is the last time I sell on here using shipping.