VM Explorer cannot connect to ESXI 7.0.2 via SSH

When I try to add an esxi 7.0.2 to vm explorer 7.1. (with patch 7.1.3) i get the error: ESXi SSH/SCP Error: There was a problem while connecting to "servername":22.

- SSH service on the esxi server is started

- the firewall ist open for SSH client and server

-  the entry for key algorithmus sha1 is added to the ssh_config file

What is the problem the vm explorer cannot add the esxi to the inventorry?