To get further information on what the issue may be, insert a Solution Information object under Solution in the tree, and view the contents.
Possible reasons that the solver may fail are:
Insufficient memory - You may not have enough virtual memory assigned to your system. To increase the allocation of virtual memory (total paging file size), go to (on your Windows Start Menu). Click the Advanced tab and then click Performance Options. Increase the size of your virtual memory.
Insufficient disk space - You may not have enough disk space to support the increase in virtual memory and the temporary files that are created in the analysis. Be sure you have enough disk space or move to an area where you have enough.
Corrupt product installation
License request rejected
The startup directory for cmd.exe has been overridden by the AUTORUN option and as a result causes the solver to be unable to locate the solver input files.
Solving and UNC Paths
If a Workbench database resides on a UNC path (for example, \\pghxpuser\Shares) for which you have write permissions, the Ansys input file will be written successfully but will fail to start the solver executable. To solve, map a drive to the location and then reopen the project. If you did not have write permissions, Workbench will instead write the Ansys input file to your temp directory (%tmp%) and perform a solution from that directory.