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If your Palm Desktop is, as a program on your computer, simply not opening / not starting up, then you will need to uninstall it (after backing up what files on it are yours), restart your computer, then install the Palm Desktop anew from a new source, e.g. this one:
If it is your Palm device that is not accessing, then you may have a problem with your Palm device, not the Palm Desktop software. Try a different USB port, a different USB cable, and see if that helps. And let me know the details, what device it is, and so forth, if that is the case. Thanks.