Try to clear your wallet's cache by following this tutorial: https://support.bitpay.com/hc/en-us/articles/360000242443-How-do-I-Fix-My-Wallet-if-it-is-showing-the-Wrong-Balance-and-or-Transaction-History-
Meanwhile you could also access your wallet by importing it to another wallet. I believe bitpay uses BIP39 so your seed should work with electrum.
Tutorial: https://bitcoinelectrum.com/restoring-your-standard-wallet-from-seed/ (Don't forget to tap options--> BIP39 Seed)
This step should be done first before reaching out their support.If this method or advice doesn't work then that's the time we would reach out into their support related to the issue and as being said they do only need 6 confirmations to be credited and displayed but checking out it do already have 12 confirmations then it should really be there.They are really the ones who would able to solve out such problem. Meanwhile you could also access your wallet by importing it to another wallet. I believe bitpay uses BIP39 so your seed should work with electrum.
Tutorial: https://bitcoinelectrum.com/restoring-your-standard-wallet-from-seed/ (Don't forget to tap options--> BIP39 Seed)
