Is there an older version of NB you can direct to me to which I could use that does NOT use the original RAR date, but instead uses the download/unrar date? I use Total Commander to sort/manage files, and the recent NB, even with the keeptimestamp=1 edit, still stores files with the original packing date.
There we can see what is going wrong when it tries to call unrar. After this, download the log and look for the part that says Calling unrar and then lower it will say Unrar output. The download links for this file are clean and no user has given any negative feedback. This dll file is produced by the Alexander Roshal. Simple Unrar is an interesting free alternative to the official Winrar app for Android. In fact, you can extract almost any file that's compressed in RAR 5.0 format or lower, even those with a password (although you obviously need the password for this).
