The package form of endnote files includes both the endnote file and the data folder that accompanies the endnote file. It is convenient in the sense that one only has to move the .enlp file. The data folder must be in the same folder as the enl file. If the data folder is missing, the .enl file does not know where to find the data folder.
The new X9 (9.31) will reformat .enl files to the new 64-bit format that is required by MacOS Catalina. To do so, just use the X9 (9.31) program to open the old 32-bit .enl format file. The program will ask you whether you want to reformat the file. If you say yes, it will create a data folder and a .enl file with that old filename, copy the references and the search terms.
However, the X9 (9.31) does not know what to do with .enlp files. You have to look inside the .enlp folder for the .enl file and data folder. In Finder, hold the control key while selecting the .enlp file to get a dropdown menu. Select <Show Package Content>. The Finder will show the package content in a window, usually containing the .enl file and the data folder. Select and double tap/click the .enl file to show the references in the file.
In the version of Endnote X9 (9.31) released in October 2019 for MacOS Catalina, Endnote cannot open and reformat .enlp files made by previous versions. The program will give an error message saying that it cannot format the file. To reformat the file, you must select the .enl file on Finder while holding on to the control button and select <Show Package Content> in the dropdown memory.
If you double-click on the .enl file in the .enlp folder, X9 (9.31) will start copying references and then search terms to a new set of files, asking you to save the filename, followed by “converted”. You can change the file name. Then the program will create a data folder and .enl file with the new filename. There is also a checkbox to make it an .enlp file.
Occasionally, the X9 program will give you an error message saying that somebody is already using the file. If you see that, quite the Endnote X9 program, and then go back to start again. If there is already a data folder or .enl with the filename, you will be asked whether you want to replace those files.
On occasion, the program may crash after it has reformated it. This may happen if the file is corrupted, which not that uncommon. First, check the new .enl file. The new file may be okay. If it is not or is empty, go back to X8 or the previous version of X9 and use the recovery library function to repair the .enl fie in the .enlp file. After you recover the file, then use the X9 (9.31) to reformat the file.