Opened emails showing "0"

Hi,

The emails are sent successfully from sendy. I've the cron setup as well -

*/1 * * * * curl -L -s https://sendy.qsstechnosoft.us/sendy/scheduled.php > /dev/null 2>&1

Still, the opened count shows 0% in the reports.

Also, I don't understand the 1x1 pixel concept, how's the image is being sent in the email. Is that possible that the email is missing while sending the email.

Sendy version is - 6.0.1.1
PHP version - 7.3.33

Any suggestions. Please advice.