Devices not being discovered usually means they are not in the same network as Homey (for instance a VLAN or connected to a repeater or Shelly extender). Another possibility is that it’s been previously added and not fully removed (for instance only one channel removed) making Homey think it’s still paired and thus not show up.
I also see some 404 errors in the log which could indicated that credentials of an already paired device have changed after pairing. This is unrelated to the Shelly 2.5 not being discovered but also something to look into to.
