I'll help you fix this, Peter3605.

Once you change the email address of your customer, QuickBooks should also automatically update the email on the recurring transactions. It could be that the stored cache and cookies in the browser are the root cause of this strange behavior. To rule this out, you can try accessing your QBO company using a private or incognito window. Here are the shortcut keys:

• Ctrl + Shift + N for Google Chrome
• Ctrl + Shift + P for Firefox & Microsoft Edge
• Command + Shift + N for Safari

If it's now working well, go back to their regular browser and then, clear its cache to delete the accumulated junk files and start over fresh. You may also switch to other supported web browsers to further isolate the issue. 

In addition, I recommend reading this article to learn how to duplicate, edit, and delete a recurring template in QuickBooks Online: Create recurring transactions.

Don't hesitate to drop a reply below if you have any other concerns or further questions. I'll always have your back.