Why it happened ?
It is probably because you did not attach the license file or your license is already expired.
Where can I attach or check my License file information?
1. Open the System administration > Setup > Licensing. Here have two menuitem you can choose.
(1). License configuration :
This is use to control which function is user can use or not.
(2). License information :
This is use to attach license file and you can check when will this license expired.
2. Click the License information.
(1). In this Form, you can click the button " Load License file " to attach the license file.
After you attach your license file by click button " Load License file ", and click "OK" after you browse the license file. System will ask you that want synchronize now or not.
If you choose " no ", when you open AX development workspace, you will see the Data Dictionary node in AOT is red.
If you choose " yes ", then the synchronize will start and when you open AX development workspace, the Data Dictionary node in AOT is not red. (The synchronize need take some time.)
(2). And also can see when will the license expired in the field " Expiration date ".
If your license file is already attach and is not expired, then your AX development workspace should can be open now !