Every block found by the pool needs to be confirmed before the pool is rewarded. That means a certain amount of blocks should pass after this block.
Please check the "Blocks" section of the pool to check how many blocks are required for a particular coin. For example for Bitcoin Gold 100 blocks are required. 10 minutes per each block on average = 20 hours are required so the balance transfers from Unconfirmed to Unpaid.
Block confirmation requires a different time for each of the coins.
2Miners mining pools: https://2miners.com/
2CryptoCalc mining profit calculator: https://2cryptocalc.com/