SHOTPlus™ 5 files are NOT compatible with SHOTPlus™ Version 6. As a general rule, you should only open SHOTPlus™ files in the version that they were created in.
You can, however, import and export data between the two versions of SHOTPlus™. For example, you have started designing a blast in SHOTPlus™ 5 and you are now using SHOTPlus™ Version 6, you can do a Text Export of the design data already completed from the File - Export - Text file option. This data can then be imported into SHOTPlus™ Version 6 by going to File - Import - Text file.