OJS 3.5.0-3 user signup error

User signup error on latest version of OJS (3.5.0-3). When users signs up, I see this error:

Fatal error: Uncaught Symfony\Component\Mime\Exception\LogicException: An email must have a “From” or a “Sender” header. in /home/customer/www/[myjournaldomain.com]/public_html/lib/pkp/lib/vendor/symfony/mime/Message.php:132 Stack trace: #0

Other emails, for example password reset, work ok, and principal contact is set at site and journal level.

Any help appreciated.