Cobo Vault firmware version V1.2.1 (BTC-Only) will allow you to use BTCPayServer as a watch-only wallet once BTCPayServer has released its next update.
1. Cobo Vault Essential or Pro upgraded to firmware version V1.2.1（BTC-Only）or later version
2. Computer with BTCPayServer installed
3. MicroSD card (FAT32 format with capacity not exceeding 32GB)
Pairing Cobo Vault with BTCPayServer
1. Insert your microSD card into Cobo Vault.
2. In the Cobo Vault hardware wallet, go to [Settings], touch [Watch-Only Wallet], select BTCPay Server], then touch [Next].
3. Touch [Export Wallet], then [Export]. Your wallet's master public key file will be exported to the microSD card.
4. Enter the wallet.
5. Take the microSD card out of Cobo Vault and insert it into your computer.
6. Run BTCPayServer on your computer, click [STORES > General settings > Derivation Scheme > Import from...] in turn, and select [Import Hardware Wallet].
7. Click [Choose File], find the wallet file in the root directory of the microSD card and click [Open].
8. Click [Submit > Confirm] in turn.
9. Select [WALLETS] tab and check the paired watch-only wallet.
And you are good to go!