Zerotier installed on raspiblitz - but not working

Hi, I am kind of a beginner, so thank you for trying to help.

I have installed zerotier through the menue of raspiblitz.

It does not connect (gives error-msg: *** ZeroTier appears to already be installed.
/usr/sbin/zerotier-cli: 1: /usr/sbin/zerotier-cli: Syntax error: “(” unexpected)

When I try this: sudo zerotier-cli join [my.zerotier-id]
I do get this:
/usr/sbin/zerotier-cli: 1: /usr/sbin/zerotier-cli: Syntax error: “(” unexpected

Seems to be an error or buggy so I wanted to deinstall and install again via debian/linux cmd-line with ```
curl -s https://install.zerotier.com | sudo bash

Result: same msg shown above - "*** ZeroTier appears to already be installed.
/usr/sbin/zerotier-cli: 1: /usr/sbin/zerotier-cli: Syntax error: "(" unexpected)"


Can someone help or does someone know what is causing this error? 

Thank you!