This is an internal Citus function can only be used in a distributed transaction

After I remove all node and plan to add node (use another ip and port but still the same server)
I get a mistake. Although I removed the database and recreated database and citus extension, I still get the error

```
test_citus=# select master_add_node('10.50.208.240', 22012);
WARNING: This is an internal Citus function can only be used in a distributed transaction
^CCancel request sent
ERROR: failure on connection marked as essential: 10.50.208.240:22012
test_citus=# select citus_add_node('10.50.208.240', 22012);
WARNING: This is an internal Citus function can only be used in a distributed transaction
ERROR: failure on connection marked as essential: 10.50.208.240:22012
```

Can someone tell me what's going on or how to fix it？this might be a small problem
thank you!