Could be a Problem, with the IP address. Maybe two devices in the network getting the same IP.
Try out to use a Static IP. To do so go to Settings > WiFi and click&hold on your network. Then choose Modify network. Tick advanced settings and change IP- configuration to static. Your IP-address should look like 10.0.0.xxx or 192.168.1.xxx. Instead of xxx type something high, e.g. “99”. For the gateway you need to insert “1” instead of xxx. Probably you need to copy the gateway-IP to DNS 1 also.
Tip: To findout your IP, open cmd in Windows and type “ipconfig”. The computer also has an IP like 192.168.1.xxx.
Edit: To make sure the IP is always reserved for your FP you can enter the IP into the router’s DHCP leases list. Then you can use any IP you like (doesn’t have to be a high one like 99).