So when you ping your domain name you don’t get your actual public ip address. Your domain is listed in the domains (in webadmin) and the dns configuration says everything is OK.
Check tools > logs. I have a log entry everytime dyndns has updated the ip address and if it fails I get an email in the administrator account.
You can ping dyndns of yunohost so connection seems fine.
May be the dyndns app is not working correctly or lost its settings. From here I’m unable to help. I never tried to explore it.