This unexpected behavior can be caused by too much cache, User48340. I'll help you send the emails.
To start with, let's open QuickBooks Online using an incognito window. This is the best spot to isolate web issues. From there, try to send the emails. If you're able to do so, go back to the main browser, then clear the cache. Deleting them is part of the browser hygiene. This prevents the program to behave differently.
Alternatively, using a different browser, like Google Chrome or Mozilla Firefox, can fix issues like this.
Please keep in touch with us if you need more help. We're just right here for you.
