Help with bounced emails

Last week over 700 of my mailerLIte emails bounced. All but 6 were to iCloud accounts. They all showed opening 5 out of the past 13 emails. A couple had opened 6 emails. I’ve been back and forth emailing mailerLite to no avail. I feel like I’m talking to AI. I can’t find a number to call them. Any thoughts on this? I am not technically savvy! I reached out to my webmaster and he doesn’t know anything about #mailerLite. @Thomas Umstattd Jr. Thanks for your help.