"Parcel#69187021534 is invalid, China Post has not received any parcel associated with !" means your seller has not shipped anything yet. If you just got this number, wait one week and track again. If over one week and it is still same result, you should open dispute to ebay for refund.

Quote from hotranjeet on October 19, 2017, 08:16
RG620413271CN
help regarding this tracking no. about status.

http://track-chinapost.com/startairmail.php shows the parcel was rejected in Shenzhen customs. Not sure the reject reason. If you purchased from ebay/aliexpress, you should open dispute for refund.

Quote from Trombas on October 20, 2017, 14:36
OK, so... I have contacted my seller at Ebay and he answered with this message:

"I’ really sorry to tell that we sell it at a really low price, so we’re unable to buy a tracking NO. for this transaction.
As you know, the tracking NO. is more expensive than the item itself.
Hope you can understand it.
The tracking no you see is used to prove that we’ve sent it out already, not for tracking
And please don’t worry, we do have a compensation in case that you can’t receive your item.
Is it acceptable for you?"

Should I believe him? or is a fraud?

69187021534 is invalid number. your seller has not shipped anything. I think you should open dispute to ebay for refund.