Hidden cells principally are no longer exported with the export action "Selected area". However, hidden cells are processed by the export actions "Table sheet" and "Workbook", too.
A new entry in the ini file allows for the setting whether included but hidden cells of a selected area with export formulae shall be exported or not: SelecthiddenCells=True or False, respectively.
The read and write functions of IDL.CONNECTOR are no longer developed since release 2016. Running Excel worksheets may be continued to be used, however, there will be only limited support by IDL. Now only IDL.XLSLINK is supported for these purposes. Only IDL.XLSLINK can be used in connection with the 64 bit version of MS Excel. IDL.XLSLINK requires at least the version Microsoft Excel 2007.
If you have many and extensive Excel maps with IDL.CONNECTOR formulae the transition to IDL.XLSLINK may be a major project. In this case it is recommended to arrange support by an IDL consultant.