The terminal stays at "Announcing ourselves..."

I was just trying out the go-libp2p examples chat-with-rendezvous, I want to modify the example to complete the data transfer, I tested it for a few days, and then suddenly my nodes couldn’t find each other.
The terminal stays at “Announcing ourselves…”.

Then I tried to use a pubsub chat at that time. After a day of testing, the same problem appeared, and now the terminal stays at “Searching for peers…”
The system suddenly cannot discover peer nodes, and then from the first time it cannot discover the peer, and never succeeds again