Please help me figure out why this transaction has not been confirmed.

The fees paid for these transactions are much lower than the value paid for recent transactions added to the block. At the time of writing this answer, the fee paid to enter a block is at least about 25-30sat/vB. The fee paid for this transaction is 10 sat/vB.

To confirm a transaction, you must use a mechanism that increases fees, such as RBF or CPFP.