There are some cases when JChem for Excel closes unexpectedly. After Excel is closed the following dialog appears:
If you press No, JChem for Excel operates further normally after launching it again.
If you press Yes, the JChemExcel.Functions add-in gets disabled, and the JChem tab doesn't appear in Excel. To enable it again please follow these steps:
1. Go to File/Options/Add-ins and at the bottom of the dialog open the Excel Add-ins list, select the Disabled Items
2. The following dialog opens:
3. Select the jchemexcel.functions from the list and press Enable.
4. Launch Excel again, JChem for Excel will work properly, the JChem tab will appear correctly in Excel.