Why "sometimes" I cannot see shared folder in other computers in my Network?

I have 2 Windows 11 PCs. One of them (PC2) has a shared folder. Many times PC1 can see this PC2 and its shared folder no problem and can copy move delete files there as well. But sometimes PC2 is simply not showing in the Network section of PC1. PC1 and PC2 are both wired connected to the same router. I rebooted PC1 and PC2 and nothing changed.

Some other times, the shared folder of PC2 was showing normal in PC1.

Why is that?