Sites cannot communicate with each other?

I have two websites:
site1.dvl.to (php 5.6)
site2.dvl.to (php 8.1)

I have a php script on site1.dvl.to that do a curl request to site2.dvl.to (with CURLOPT_SSL_VERIFYHOST and CURLOPT_SSL_VERIFYPEER set to false).
I get the following error:
cURL error (7): Failed to connect to site2.dvl.to port 443: Connection refused

If I ping site1.dvl.to and site2.dvl.to via shell.sh of devilbox, they ping correctly.

Any idea what is wrong?