Any account with a lock beside it is a system Xero account. These accounts can no longer be used with Vend as these types of Xero accounts restrict transactions or journal entries posted to them. Check out this article to find out more about Xero's locked system accounts.
If this is the case, you will need to create a new account code that matches that account's setting. To learn how to create a new account code, check out this article.
Once you have set up the new account code, go into your Xero settings in Vend and click Sync from Xero in the 'Accounts' section at the top of the page to refresh your accounts to select the newly created account.
If you need any extra help with this please sign in here to contact Vend Support and our Support team will be able to give you some additional assistance.