I sent Bitcoin transactions two days ago, nearly 48 hours ago. So far they still show as "Unconfirmed transaction". I set the fee as 8 satoshis per byte, with the total cost to be 0.0000081 BTC. According to this site
https://bitcoinfees.earn.com it should take between 25 mins to 480 minutes (8 hours) to be confirmed at 8 satoshis per byte. From their graph there's 2,433 transactions in the last 24 hours with that same fee. What to do and why hasn't it been confirmed yet?
You just got unlucky!
Really really unlucky!!
You've sent your transaction when the mempool was quite empty and normally the tx would be accepted but just then a wave of transactions hit the chain, see the red circle.

We had quite an unusual morning with a lot of transactions, there was a lot of bad luck with miners, yesterday we were behind by 11 blocks so this happened.
You either wait or you try a CPFP transaction.
PS.
bitcoinfees.earn.com sucks!