When you get a very high reading, like the
100 kohm reading, it is very likely that there
is absolutely no connection between the skin
and one of the electrodes in the pair (red in this
case, since pink to blue is OK, you know the
pink electrode attached to the nasion is OK).
    It is possible that the red electrode has
fallen off.  If that is not the case, the electrode
may have a broken wire in it.
    Always handle the electrodes carefully.
The common places for the electrodes to break
are at the connectors.  When you insert and
remove the connectors from the physiologic
amplifier, be sure to pull straight up,
and hold the bottom-most portion of the
electrode where it is reinforced with the
connector.  The portion where the electrode
connects to the wire, near the cup, is also
a place where it can fail.
    If you want to test to see if you have a
broken electrode, you have two options.
Replace it with a new electrode, or do a
real test.  Place two electrodes in a cup of
water and test the continuity.  If it still reads
a very high number, the electrode is broken.
The cup of water will carry the measuring
current from the two electrodes very
efficiently, you should read a very low value.