I have an issue with my MacBook Air.
It won't connect to my home internet but strangely enough it will connect to my iPhone and my sistes Mac Air but not mine.
Is there any solution?
Your wifi is either turned off or Kaput !!=(Broken and useless; no longer working or effective.).
The connection to your sisters iPhone and to her Mac is not done by WiFi, she is sharing Internet with you.
Go to system preferences and disable the Internet Sharing to test.
Check that your WiFi is turned on.