It appears that subdomains txt records are taking ages to become available. With domain records, I do not have any issues, it gets available really fast. I am trying to add a global Let's Encrypt certificate for a domain, and it asks me to create a subdomain txt record with _acme-challenge.domain.com
How much does it take normally? Because in Plesk if I click Continue without this being available, it breaks everything and I have to start from scratch, with a new TXT code being generated and changed...
Usually changes will take effect within 15-20 minutes, but it can sometimes take up to 48 hours for the changes to propagate fully worldwide. Looks like your previous settings were not correct and our chat support was able to address that for you.