Try this.
Edit file /usr/local/hestia/web/fm/configuration.php and replace this:
shell_exec("sudo chmod o+x " . quoteshellarg("/home/" . basename($v_user) . "/.ssh"));
by this:
shell_exec("sudo /usr/local/hestia/bin/v-change-fs-file-permission " . quoteshellarg(basename($v_user)) . " " . quoteshellarg("/home/" . basename($v_user) . "/.ssh" . " 0755"));