Issue Description
Archicad 10 thru 26 will open Archicad PLN files going back to version 8.1. For files older than 8.1 you will need to open and save them in Archicad 10. Then this newly saved Archicad 10
!IMPORTANT! Due to changes in macOS the File Converter mentioned here no longer works on recnet versions of macOS. Please contact Technical Support if you use macOS and let us know you have files you wish to have converted to a newer version which can be read by recent versions of Archicad.
Solution
Archicad 10 File Converter works on all recent versions of Windows. It worked on macOS 10.13 and below. Use this converter to up-save any 6.5, 7.0 or 8.0 PLN file to version 10.
1. Download the ARCHICAD 10 USA for Windows package from here: https://dl.graphisoft.com/ftp/techsupport/downloads/fileconverter/AC10-USA-1209-WIN.zip
2. Once downloaded, double-click the ZIP file to extract it to a folder.
3. You can keep this folder anywhere on your system.
4. Double-click the "Archicad" app inside the folder to launch Archicad 10.
5. Choose "Open a project" and click "Browse" to locate the file you wish to open.
6. Open the file and once past any warning dialogs
7. Choose File > Save as... and add a suffix, such as "v10" to the file name so that you keep your original file intact. Example "Smith Residence v10.pln"
8. Now close Archicad 10 and you may open the re-saved copy of the file in any recent version of ARCHICAD ( 26, 25, 24, etc.)