Why am I not able to go onto the internet?

Hi all! So here's the thing ever since I bought this laptop of mine, i had problems with connecting it to the wifi. I have tried to do the prompt and whatever but it still won't work. It says I'm connected to the internet and have a strong signal, but when I go onto the browser it automatically disconnects and says "can not connect to this network". I tried to troubleshoot it, but it didn't work. It told me that there was something wrong with the access point or my router. Though, it can't be my router because all other devices are able to connect to the network no problem. I even tried connecting to other networks as well but it still gives me the same message. I've brought it into the repair shop and they claimed the problem was fixed but it wasn't -.-

Any tips will be appreciated. Thanks in advance.