Allow me to take over and help you set up the alignment when printing checks, BargeProperties.
In QuickBooks Online, you need to use voucher-style pre-printed check stock, with the check on the upper third and a stub in the bottom two thirds.
Your 3-part check won't align since it's no longer supported in the system. I suggest using QuickBooks compatible checks for your daily transactions.
You can order through QuickBooks Checks & Supplies. Just hover your mouse's pointer on the Phone icon to get the number. Or check for a third-party solutions that QuickBooks offers.
Here's also another way of setting up the alignment in QuickBooks Online: Align preprinted paychecks.
Stay in touch with me if you need additional information about printing checks. I'm always right here to help