Xero has set a limit for how many times we can call its API. When this limit is reached, the error message "Xero API call rate exceeded" appears.
In this case, you’ll need to wait until it’s gone.
If the error is HTTP TooManyRequests - Too many requests in the last minute (minute), you need to wait a few minutes before retrying your actions
If the error is HTTP TooManyRequests - Too many requests in the last day (day), you need to wait 24 hours before attempting further synchronization
Note: it is advised to disconnect the organization for at least 24h to ensure the API rate limit will not be constantly exceeded.