And see if you only have 3 rules (input, forward and output) with only ACCEPTED and no other lines.
If not, then some part of the firewall is still active, maybe the build in from Centos 8.
/usr/local/bin/curl returned error code 8
curl: (8) Failed to connect to port 21: Connection refused
FTP information invalid. https://100001.onl/https://1921681254.mx/
I use Centos 8 and disable firewall but not working. With Centos 7 work fine.