wifi connection is not working
Hi everybody. it's my first time in the Apple Support Community!
Few weeks ago I notice my iMac (10.10.4, mid 2011) is not connecting to my home wireless wifi when I switch it on.
We have many devices connected to that wifi network, some smartphones, a laptop and an iPad, and all of them work properly.
I've noticed that everytime I switch on my laptop and it connects to the wifi, then my iMac connects too. Never (almost) before that.
I have tried to reset the router, changing passwords and some other things but it still working wrong.
Has someone suffered something like this?? How can I fix it??
Thank you a lot for advance. Regards! Vi
iMac (27-inch Mid 2011), OS X Yosemite (10.10.4)