Q: Cannot connect to external display through HDMI

Did you go to System Preferences > Display click the arrangement you want, mirroring or not however you want to display.

The Displays window should have a button that says Arrangement, but since yours doesn't it is not detecting the external display.  Sounds like one of the cables is not allowing communication properly.

That very well could be the TV or more likely the settings on the TV...I connected my MBP, 15", i7 running Lion 10.7.5, to a Samsung LCD TV this weekend.  Went to the Apple store and bought the Kanex Mini-DP to HDMI Cable, Part Number H4637ZM/A ($44.95) and the Apple Mini Displayport to VGA Adapter-INT, Part Number MB572Z/B ($29.00).  Both worked with the MBP and Samsung.  I had to go to the Samsung on-screen menu to select the input source for each, HDMI and PC so it would "see" the MBP.  On the MBP, I opened System Preferences > Displays and the displays window showed three buttons top center...middle button was Arrangements which allowed mirroring to be used.  Also slected resolution for the VGA to be 1980xwhatever it was for the TV.  Both gave very sharp images using Keynote iWork presentation software.

The source selection is necessary on the TV, but I do not understand why your MBP is not giving you the Arrangements button in the Displays window...there is a breakdown in communication there, the MBP is not recognizing the TV.  That should occur irrespective of the settings on the TV.

Does your TV support VGA input?  If so, can you find someone to lend you the Mini-Display to VGA adapter so you can connect that way and see if the two communicate?

I doubt the issue is my use of Lion vs your use of Mountain Lion, but since I also have ML on the MBP I may just go and reboot into ML and try it that way to make sure the issue is not ML itself.

Same problem here

MBP early 2011

Samsung TV and Monitor

Neither HDMI or VGA cables work

OSX 10.8.2

Ok, thought I'd chip in here as I've just got back from an appointment at the Apple Store Genius Bar to address the same problem with my April 2011 MacBook Pro. It's Mini Display Port has never worked when connecting to an HDMI tv set though I use it constantly with a Display Port compatitble third party external monitor. I've run OS X 6.8, 7 and 8.2 and it's had no effect, any set I connect to will not see my MBP.
They wheeled out an HDMI tv (it was a generic set and not a brand I'd heard of) to connect to, logged into my MPC with Apple's remote diagnostic tool and found no hardware or software issues.  They changed around the leads 3 times and none of them worked. One of the Genius then plugged what looked like a 13 inch 2012 Macbook into the the tv and on the second lead (one of 2 identical iWires taken from the shop display) it worked.

The Genius' take on it was that they'd never had anyone come into the store with this problem and that it's the first he'd heard of it. He also said that there is no mention of HDMI compatiblity in any of Apple's tech docs or manuals for my machine and that Apple have never claimed HDMI compatibilty with Display Port.

One hypothetical solution would be to completely replace the logic board but that wouldnt work as all we'd be doing is replacing a logic board that according to the Apple diagnostic tools is working perfectly for an identical one. Apparently Apple made no changes to the logic board for that computer.

Macbook Pro, April 2011

OSX 10.8.2

I am having similar problem connecting to an external monitor (mini Displayport to HDMI).

I tried connecting it to my TV to see if the monitor was incompatible. My macbook connected to the TV and the TV doesn't recognizes it, it says "check signal cable." I tried it with my new iMac (Late - 2012) the mini Displayport works fine, but it will not work with my macbook pro (Newest Model).

You should get the INSIGNIA brand Mini Display HDMI Adapter. The AUVIO is for PC and not for MAC from my understanding. I was having the same issue using an AUVIO and just went and got the INSIGNIA for MAC and it worked perfectly first try. Hope this helps.

I had a similar problem once.

It turned out that there was dusts in my thunderbolt port so the adapter was not making a good connection with the Macbook Pro.

The solution was to blow out the Macbook thunderbolt port with a can of compressed air. Make sure you power off the Macbook first.

This is the adapter I used

https://www.amazon.com/Sabrent-DisplayPort-Thunderbolt-Adapter-DA-MDHA/dp/B017NK IQ8M/ref=sr_1_38?ie=UTF8&qid=1473104620&…