campaign sending stucked in "pending-sending" status


I am using mailwizz latest version I have already added 7 SMTP delivery servers and assigned them to 6 customers. Today, i added 1 new SMTP and created new customer account. Now, when i am verifying new SMTP, it is working fine but while scheduling campaign with new customer account, campaign stuck in "pending-sending" status. i checked application log and found following error

"[error] [application] Cannot find a valid server to send the campaign email, aborting until a delivery server is available!"

I tried to figure out issue, cron jobs are fine. since, i am able to schedule new campaign with old customer accounts.

Any help would be appreciated.