Had a package returned to china from US customs for unknown reason EB787430946CN. Been stuck for 2 weeks just sitting at import customs. Seller continues to not be helpful... any idea what's going on?

My package that I've sent to China is a return for a refund. It has been stuck in customs Shanghai for 18 days...tracking no. RN672604651GB what is going on? Please help.

Hello, I sent a package through USPS to China back in November of 2021. It has made its way to China, however has been stuck in customs since December 9th, 2021. There has been absolutely no movement and I have no idea how to contact China customs to see what I need to do. My items are not prohibited, so I’m not sure why they are being held. I may need to pay a customs fee but I need help on figuring out how to do so. The tracking number is USPS CJ190449362US.