Zerotier service not running on TP-Link with OpenWRT

I have flashed TP-Link C6 router with OpenWRT 21.03. Installed zerotier. After every restart if I run any command with “zerotier-cli” I get following error. Restarting the service (/etc/init.d/zerotier restart) seem to resolve the issue, however, apparently it works until next restart. Any advise on fix will be appreciated.

Error connecting to the ZeroTier service: connection failed.
Please check that the service is running and that TCP port 9993 can be contacted via 127.0.0.1