The transaction might be dropped due to following reasons:

1. Setting up a low gas price while submitting the transaction.

2. Sudden surge in the gas price due to congestion on the Ethereum Mainnet.

3. Transaction is canceled by you from your wallet or replaced with a new transaction.

You can proceed with the dropped transactions in the following ways:

1. If your transaction is stuck for more than an hour, a Try Again button will be shown. You can click on the 'Try Again' button to complete the same transaction. You can refer to this video for more information on how to use the 'Try Again' feature.

2. Please check your Metamask wallet as well because sometimes transactions might be dropped due to queued-up transactions in the Metamask. In that case, clear the queued-up transactions or re-install the Metamask in the same browser.
3. You can install the Metamask in an alternate browser and then try to complete the transaction using Polygon Wallet Suite.
4. You can use this link as well to complete the pending withdrawal transaction. 
Paste the transaction hash in the search option and click on the Confirm Exit button to complete the transaction.