I am not able to send Imessages or FaceTime on my iMac.

Question

So about 3 days ago All of the sudden my Messages and Facetime app no longer work on my iMac. I can login to both but if I try and send an Imessages I get "Not Delivered". I will NOTE that I can use the screen share option and SMS messages send but only to people in my contacts that do not have Imessage on their device or do not have it activated. I know that Text Message Forwarding may be helping with this part.
Also to note that Messages and Facetime are both currently working on my Iphone 6+ with no problems with same account
As for my Facetime I can also login but if i try to make an audio/video call it automatically says "Call Failed" as if it is not even trying to connect.
Things I have tried:
     1.) Logging out/in of my phone and computer (all devices).
     2.) Restarting my computer.
     3.) Resetting my PRAM (restart holding command + ALT + P + R) during boot up.
     3.) Deleting plist files (NetworkInterfaces.plist, com.apple.airport.preferences.plist) in Library/Preferences/SystemConfiguration then restarted my computer.
     4.) I have also tried resetting my iCloud account password.
     5.) I reinstalled Yosemite on my computer but it did not help.
Please Help I am a Web Developer and use Messages to stay in close contact while working on projects. It makes sending URLS to clients and the other business owner simple and also makes it easy for me to communicate with my brother while developing without having to be on the phone.
iMac (27-inch, Late 2013)
I am using Yosemite Version 10.10.2 (14C109)
and Messages Version 8.0 (4733)
and Facetime Version 3.0 (2151)
I have a feeling there is some kind of network issue or bug on my computer.
Thanks in advanced for the Help!

Answer 1

Back up all data.
Quit FaceTime and Messages if they're running. Force quit if necessary. After each of the following steps, restart the computer, then test. If the problem isn't resolved, quit again and go on to the next step.
Step 1
Make sure you know the ID and password you use with FaceTime and iMessage.
Launch the Keychain Access application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad and start typing the name.
Select the login keychain from the list on the left side of the Keychain Access window. If your default keychain has a different name, select that.
If the lock icon in the top left corner of the window shows that the keychain is locked, click to unlock it. You'll be prompted for the keychain password, which is the same as your login password, unless you've changed it.
From the menu bar, select
          Keychain Access ▹ Keychain First Aid
from the menu bar and repair the keychain.
From the Category list in the lower left corner of the window, select
           My Certificates
Look carefully at the list of certificates in the right side of the window. If any of them is marked with a red "X" as expired or invalid, delete it.
Now select
          Keychain Access ▹ Preferences... ▹ Certificates
There are three menus in the window. Change the selection in the top two to Best attempt, and in the bottom one to  CRL.
Next, select
            Passwords
in the Category list. Enter "ids" (without the quotes) in the search box in the toolbar of the window. Delete all items of type "application password" that have a name beginning in any of the following ways:
            ids:
            IDS:
            com.apple.ids:
Also find and delete all items with "facetime" or "com.apple.idms" in the name.
Step 2
Hold down the option key and select
          Go ▹ Library
from the Finder menu bar. Move the following items from the Library folder to the Trash (some may not exist):
          Application Support/CallHistoryDB
          Caches/com.apple.imfoundation.IMRemoteURLConnectionAgent
          Caches/com.apple.Messages
          Containers/com.apple.AddressBook.FaceTimeService
          Containers/com.apple.AddressBook.FaceTimeService
          Containers/com.apple.corerecents.recentsd
          Containers/com.apple.FaceTime
          Containers/com.apple.soagent
          IdentityServices
Leave the Library folder open.
Step 3
In the Preferences subfolder, there may be several files having names that begin with one of the following strings:
          com.apple.facetime
          com.apple.FaceTime
          com.apple.ids
          com.apple.im
Move them all to the Trash.
Also in the Preferences folder, there is a subfolder named "ByHost". Open it and do the same thing.