how to reusing point

[alicera]

1. primary is broken (node1)
2. standby promte (node2)
3. unregister old primary (node2)
   It will show

ERROR: 1 other node still has this node as its upstream node
HINT: ensure these nodes are following the current primary with "repmgr standby follow"
DETAIL: the affected node(s) are:

4. standby follow (node3)

DEBUG: local tli: 1; local_xlogpos: 0/B5ACDC8; follow_target_history->tli: 1; follow_target_history->end: 0/B5ACDC8
INFO: local node 3 can attach to follow target node 2
DETAIL: local node's recovery point: 0/B5ACDC8; follow target node's fork point: 0/B5ACDC8
DEBUG: replication slot "repmgr_slot_3" exists but is inactive; reusing
NOTICE: setting node 3's upstream to node 2
WARNING: node "node3" not found in "pg_stat_replication"

The step 3 and 4 are fail .
how to fix it