Inspiron 5759 internet not working and modem does work on other devices

Inspiron 5759 bought in 2015 and has always worked until today.It does not connect with the internet.It has to be related to the computer itself I think because other devices - cell phone and kindle - connect to the wiFi with no problem. Internet diagnostics does not run it just sits there and says ”starting diagnostics”. After an hour I turned the diagnostics off because it never got beyond "starting". The Function button for internet/PrtScr is turned on to internet. Any suggestions... Thank you.