Hi @Billfred12 ,
Successful casting means there is some functionality in your internal/LAN network which is normal and expected, and confirms the WiFi connection is successful. With the casting test performed, there is no need to check access to the router management page which only confirms the same thing, that there is internal/LAN functionality.
On a device which can successfully connect to WiFi but claims it has no internet access, I would recommend to visit the IP address 142.250.187.238 in a browser which should be one address which google.com resolves to (shown below).
There are two primary ways a device will check whether internet is present, it may check that it can ping a well-known IP address (e.g. Google DNS 8.8.8.8), or it may check it can ping some domain name (e.g. connectivitycheck.alive.com) which also requires successful resolution of the name to an IP address before it can perform the check. By taking the above advice to access an IP address directly, you side-step the need to perform name resolution.
[x@x ~]$ nslookup google.com
Server: 192.168.x.1
Address: 192.168.x.1#53
Non-authoritative answer:
Name: google.com
Address: 142.250.187.238
Name: google.com
Address: 2a00:1450:4009:819::200e
