Due to the extremely high fees on chain currently. many transactions are not confirming. Subsequent transactions that rely on the outputs from these "stuck" parent transactions are failing to be accepted by the mempool due to low fees applied to them and the parent transaction outputs being unconfirmed. As this is the case, BitGo recommends that users experiencing this issue use the accelerateTransaction endpoint of the BitGo API to increase the fees applied to the parent transactions, allowing them to be confirmed on chain. The following site can assist in reviewing the BTC mempool to allow for the determination of the fees to be applied to these parent transactions: https://jochen-hoenicke.de/queue/#0,24h
The accelerateTransaction endpoint of the BitGo API is documented here: https://app.bitgo.com/docs/#operation/express.wallet.acceleratetx
Please be sure to specify the parameter cpfpFeeRate in the call to the accelerateTransaction endpoint. Additionally, you may wish to also specify a value for the parameter maxFee in the call to limit the total fees applied. This value should be expressed in satoshi.