If you order checks online it can take a day for the checks order to be processed and then printed.
Some check ordering websites print the checks the same day and ship the same day.
After the check ordering website company ships the checks it can take 2 to 7 days to get the new checks in the mail.
If you order the new checks from your bank it can take 4 to 7 days to get the checks in the mail as well.
Usually in my experience I get the checks in the mail from my bank after 5 days.
If you haven't gotten your checks in within 7 days then you should call your bank or contact the place where you ordered your checks from to see what is going on.