Failed to detect a change in your network settings.

Hello @williasthomas192004 ,

I found a KB related to your issue. Can you try the solution mentioned in the document? 

https://community.fortinet.com/t5/FortiNAC/Technical-Tip-Captive-Portal-Registration-Failed-to-detect-a/ta-p/222736

Once the VLAN has be changed FNAC normally sends a trap to the switch to bring down the related port then another trap to bring it up again. This will force the client (without PA) to resend a DHCP request.

In your case this SNMP step has failed, and it is usually a misconfiguration in SNMP. Check if it is RW and if snmpwalk is returning information, otherwise fix it then redo the test.

Edit: Ignore this suggestion. Didn't notice this is WiFi

Is this Windows host connected on the same SSID as the working Android or is it a wired host?

Since the supplicant in the end host is not used in this case (MAC authentication), the host is not aware of any network change until a port bounces or a SSID disassociation happens.
You need to check through the FGT logs, what happens with this host status after a CoA/DM is received by FNAC.