Due to the nature of digital currency protocols, transactions cannot be cancelled or altered once they are initiated. This is what allows merchants to accept digital currency without the risk of chargebacks.
Again, how long does it take for Bitcoin to confirm?
about 10 minutes
Whatever the case may be, why are BTC confirmations taking so long? Transactions are being added to the bitcoin mempool's full queue constantly. Some may have been sent with higher miner fees than the one sent with your payment. This means that with current network traffic, miners may deprioritize your unconfirmed transaction even if it was sent with an appropriate fee at the time.
However that may be, how long does a pending transaction take on Coinbase?
The main reason for a pending Bitcoin transaction on Coinbase is because the Bitcoin network is congested. It's usually nothing to worry about and your transaction should clear within 1-2 hours. If you don't receive your transaction within 24 hours, contact Coinbase's support team.
Why is my Coinbase pending?
Incoming transactions show up in your account almost instantly (within a few seconds) but will show as 'Pending' until there have been enough network confirmations. ... The number of confirmations needed is based on the digital currency.