The best way to fix this, as per how Apple tech support advises is:
1) (not advised by apple as you should have an ID). But Ensure that your DeveloperID is added to Xcode. (If it's an ID that hasn't got Agent or Admin access) then you need to make sure the you've created the correct provisioning profiles and installed them. If it is an Admin/Agent account, all's good
2) Open the project in question and:
i) Click on the target which you're having problems with
ii) Click on the "General" tab
iii) Make sure that the "Signing" is set to "None"
iv) Click on the "Build Settings" tab
v) Make sure that "All" and "Combined" levels are chosen" (see the image below, All and Combined levels are just under the main tabs on the left)

vi) Scroll down to "Code Signing"
vii) You only need to worry about the "Code signing identity". If that's filled in, click on the line and press backspace (delete) so it clears it
viii) The resource rules should be empty as this no longer applies (for general purpose use)
ix) Under Provisioning Profile, change it to "Automatic"
After this press:
1) Cmd + Shift + K to do a build clean
2) after this is done, press Cmd + B to build
If this doesn't pan out, then head back over to the "General Tab" and under the "Siging" section as mentioned in (2 iii) above, you'll see a "Fix Problems" button...
Hope this helps.
Cheers,
A