We are having the same problems, however it's not just when emailing the invoices, it's also when I go into preferences to try to switch to single user. I have contacted support on numerous occasions but to no avail. They just keep telling me to buy the upgraded QB subscription. This is ridiculous. I can't work with this, it's costing me money to investigate why this is happening, to talk to help on the phone for 3 hrs and not able to get the work done.

  Please fix this ASAP!!