Invoice E-Mail not working anymore after upgrading to 3.0

After upgrading to akaunting 3.0, my invoice mails are not working anymore. I have the exact same settings as before and double tested the SMTP configurations. Also I have get no error messages or something a like in the logs. Anyone else encountering these issues?

When I press send mail, some loading bars at the top spin, but nothing happens! Looking for advice, this is a critical issue. Happy to provide more details.

I got a small update. Once I view a shared link, i receive an email, that the link has been opened, but still not able to send them via the Popup on the invoice menu. Is there an issue in the frontend?

Hey all. I finally figured it out. When sending the mail request, I saw that the app couldn't find the path /var/www/html/storage/app/temp.

I created it manually and changed the owner to www-data. Now it works again.