As Trevor says you need a blind solver when the mount does not know where it is, a local version of astrometry.net will do this for you without going to the internet, you will have to download the various bits onto a drive and load them into the observatory computer at some time. Then when platesolve2 fails it should use the local version of astrometry.net.
Most of the time when I start up the scope still knows pretty much where it is but if I do something wrong then I will first do a blind solve then after that platesolve2 always seems to work.
You may have to set your encoders up to ignore if you want to centre accurately, with it on ignore I normally centre to within 3 pixels in one or 2 attempts. With the Lucas suggested settings you will need this at 100 pixels or more.