will not upload

I have the problem of not being able to upload
It use to work with no problems last time I used it which was months ago.
The upload arrow is dull therefore not operating.
I have tried with a Uno and also a Mega and the results are the same, upload arrow not bright.
The computer is a Mac if that makes any difference.
Are there any solutions to this problem?
Geoff

Are your boards still recognised by your OS when you plug a board in; I'm not a Mac user so can't tell you how to check.

The upload arrow is dull therefore not operating

What is the upload arrow.

Which version of the IDE?
Which version of the OS?
Bad cable? Try another one.
Bad contact? Cable properly inserted at both sides?