It's a bit difficult to "guess" what factors we're dealing with in this situation, but I'll try to help with the little experience I had with ADB + Mac OS. Here are some questions that can help diagnose the problem; I will edit the answer according to future information:
Situation Checklist
(1) Which version of Mac OS are you using? 10.6 ( Snow Leopard ), 10.7 ( Lion ), 10.8 ( ML ), 10.9 ( Yosemite )? Or any of them? (Maybe an older one.)
(2) Did you mention Eclipse - I believe you have downloaded the latest Android SDK and have access to all the tools?
(3) When you say "I'm trying to activate debugger mode ...", you're claiming that you've already unlocked the Developer mode by tapping quickly (7-8) times) in Build Number in "Settings > About mobile" ? (Assuming the latest versions of Android, it may vary by manufacturer and version.)
(4) What OS version do you have on your mobile phone? 4.1, 4.2, 4.3, 4.4? Is stock or did you load a custom ROM ? If stock , did you take root access?
(5) If we are a custom ROM , are you sure that it is working as it should? I've had cases where I "zoei" both the device, that I had to do a factory reset to go back to debuggar as it should.
(6) Once you have verified all the steps above, did you get to test on another machine, preferably with another operating system (with its proper drivers installed.) Like Linux or Windows ? The Mac OS does not need drivers to run the ADB on most Androids (at least not the ones I tested - Samsung Galaxy S2-S4, Moto E / G / X)
A little "Troubleshooting"
Now, let's try to address the problem.
ADB and Privileges
adb-server starts the first time you run the ./adb devices command because it needs a communication interface (eg "daemon ") to listen on a port and communicate with the OS on the mobile phone. This daemon needs privileges to write via USB and, because it is a UNIX based system, maybe your problem might be to be running adb an unprivileged local / user. Try running sudo ./adb devices to eliminate the possibility of being a problem generated by lack of privileges. - If the daemon is already running, first of all, kill the process with a kill [PID] where [PID] is the process identifier. You can figure this out with something simple like ps aux | grep adb . (If, by any chance, the process hangs and does not "die", try kill -9 [PID] .
Hardware > Software > Change of Environment
Another possible flaw in this communication may be, ironically, the cable. Test with another USB cable to make sure this is not the problem. Or, on the same line, try to mount the USB share on your device and download some files via Android File Transfer , a client developed just for this - transfer files from Android to Mac. If you can do this transfer, then your cable and communication are OK .
If your hardware check does not present any problems and there are no obvious reasons why the software does not "chat" properly, try the (6) step of the checklist. Try another system and see if everything works fine. You can use something like 15 sec. ADB Installer to prepare a Windows machine in a matter of seconds to perform your test. Without having to download the SDK all over again.
If Android File Transfer , as mentioned above, works normally but adb still does not see your device, you have one of two problems:
(1) Your cell phone is not able to emulate USB debugging
(2) Your libraries / kexts in OS X are somehow messed up
In any case, you can only help with more information. I hope I have helped in some way.
