Thanks for your feedback and using Aspose.Cells.
From your screenshot, it seems you have successfully experimented and observed the working of CellsHelper.FontDirs in your test machines.
Now the problem is specific to your production machine. Suppose you have fonts in C:\Windows\Fonts directory and there are several fonts like Arial, Times, Arial, Verdana, Annabel and CatsAlphabet etc.
And you have an excel file which uses these fonts. Now if C:\Windows\Fonts is accessible, then all of these fonts should be rendered fine and if it is not accessible by Aspose.Cells, then none of should be rendered.
It cannot happen that Arial, Times, Verdana and CatsAlphabet are found and rendered fine but Annable is not found. Since all of them are in same directory, so all of them should render fine.
Please experiment this scenario, do you see such a problem that other fonts are found from the directory but only Annabel is not found.
Please also provide us your Annabel font so that we could also experiment this issue at our end.
Thanks for your cooperation.