Since Windows 11 Upgrade I can't access some devices on LAN

[salex319]

In addition to many other devices I have 3 Raspberry Pi's on my LAN and 3 PC's. My notebook PC is the only Windows 11 device. Since the Upgrade I am unable to access some of these devices. For example at first I could SSH into only one of the Pi's. After working a while I noticed I could access a second Pi via SSH. When I try and access the third the connection times out. Pinging results in the following:

C:\WINDOWS\system32>ping 192.168.1.91

Pinging 192.168.1.91 with 32 bytes of data:
Reply from 192.168.1.175: Destination host unreachable.
Reply from 192.168.1.175: Destination host unreachable.
Reply from 192.168.1.175: Destination host unreachable.
Reply from 192.168.1.175: Destination host unreachable.

Ping statistics for 192.168.1.91:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

My PC IP address is 192.168.1.75.

The '.91' address doesn't appear when I use the "arp -a" command. The device is accessible from my other PCs. As I mentioned another of the Pi's gave me the same problem initially but then appeared on the "arp -a" listing and became accessible.

Would like to know how to make this Pi accessible.