New freedombox setup but letsencryt failed, Cockpit unreachable

My first freedombox setup on my raspberry pi 3B+ run 9 month without problems.
After the disaster to install tiny tiny rss i setup a new freedombox on a new 32GB microSD-card.
The DynDNS provider is the same as befor the new setup, even my domain name is the same. The ip address in my network is defined with dhcp and a static lease. All necessary portforwards exists in my router.
The raspberry pi 3B+ image is from 2019-07-10
After accessing plinth i see Cockpit and Sharing is now preinstalled (Why?)
then i setup under System:

  1. The administrators name and pwd.
  2. I set up Configure to my host name and domain name
  3. I set up the Dynamic DNS client.
  4. I open the Let’s Encrypt page. I receive a Certificate. I tetsted it with diagnostic but let’s encrypt failed.
    I get this error even with my old runnig setup bevor i try to install tiny tiny rss.
  5. I install ejabberd. I can access my freedombox with my tablet and my smartfone using Conversations, my user name, password and domain name. I can reach my Contacts.
  6. I try to access Cockpit with https://mydomain/_cockpit/ , i receive “Website unreachable!”
    Diagnose is OK.
  7. I try to access the freedombox with ssh (portforward port 22) and domain name, i can access the box from outside.

I tried the same procedure with an other domain name but there are the same problems.
Running diagnostics all test are ok, exept let’s encrypt and DNSSEC failed.