Second monitor as Display

Hey there

I have a new 2017 27 iMac. Upgrade from old 2010 21 iMac

When I used the old model I was able to use an old monitor I had kicking around as a second monitor. I cannot seem to get this to work on the new 2017. I did have to get a new adaptor. (i.e. VGA to Thunderbolt 3) But beyond that the setup is the same

Under System in Display the arrangement tab is not coming up.
On the second monitor it says its in power safe mode and press any key on the keyboard to continue. (Obviously its just a monitor so in order to use the keyboard I would have to be able to set it up)

Any thoughts where I might be going wrong?
Thats for the help!

My question is (assuming this monitor only has VGA video input)....why in 2017 are you still using a VGA monitor?

Your new 27" iMac probably cost $1500-$2000. Why use a used VGA monitor that probably sells for $10 bucks on Craig's List with a brand new 27" iMac (and the adapter just purchased probably costs more than the monitor is worth)?

Now if this 2nd monitor actually is a nice-good sized monitor...and has DVI, HDMI, or mini-display port video ports on it...then you really should be using the DVI or HDMI ports on the monitor...since VGA is REALLY out-dated.

- Nick

You might try using a different adapter to connect the monitor. I went through three recently before finding one that worked reliably. The first one worked for a few months then suddenly stopped. I tried that adapter with another monitor and new cable with no improvement. It worked fine with my MB Pro but not with the iMac. A second adapter was much the same although it worked with some HDMI monitors and not others.

The third adapter has performed well for about two months now. I'm keeping my fingers crossed.