Always make sure to double check if the wallet you're sending to requires a destination tag to ensure funds get credited. If you do not enter a destination tag when it is required, this will result in your funds being lost.
A destination tag is extra information included in an XRP transaction that helps the receiver to identify which user to credit a transaction to, much like a bank reference number.
Certain wallets, such as Poloniex and Gatehub, do not require you to have a destination tag when sending to their wallet. However, most exchange wallets, such as Kraken and Bittrex, require you to enter a destination tag when sending your XRP to their wallets.
To know more about how to send and receive XRP, read here.
Contact us through the Coins app or Coins Support Form should you need any further assistance.