I have search endlessly online the solution for this problem including all the previouses reddit posts, still haven’t found it yet and decided to just make a post about it.

It’s one of those problem where when I connected to Wi-Fi it stays connected for a while but after a literal minute it stated “No Internet, secured”. My other devices works well accept for this pc

I receive my dad old pc unit which is the Dell Optiplex 7020 (I know its bad, shut up we’re not rich). I use the 300Mbps TP Link USB wifi adapter. Works well before so I don’t know how theres any relation. I upgrade the CPU from i3 to i5, works well, ordered a new CPU cooler (IS-40X V2) and the problem starts emerging. I ran troubleshoot and says that “Default gateway not available” . Use every possible solution online, still haven’t managed to solve it yet.

Any help would be appreciated, thanks.