RF Gain (ATTN) indication not OK (dashes iso ATTN) on 40 and 30 meters

This is behaving as designed.  This post explains it in detail and is repeated here, below:

https://community.flexradio.com/flexradio/topics/since-v1-3-i-am-now-see-attn-on-the-screen-just-lik...

To clear up the confusion on this, let me explain how the preamp works.  In a radio with a single receiver, you can decide to use the preamp on 6m and not use it on 40m.  In the FLEX-6300, you have the option of listening to two bands at the same time.  If you choose 6 and 40, you really want the preamp on for 6 and the attenuator on for 40 for almost all band conditions.  Since there is a single SCU in the radio, you have to decide whether you want the preamp on or off.  So to accommodate listening to 6 and 40 at the same time, the preamp has slope to it that provides gain on the high end of the spectrum and attenuation on the low end.  So the panadapter reads out the effect of the preamp on the band you are on.

To expand a little further, the necessity for a preamp diminishes as frequency lowers because of the atmospheric noise present on the bands.  You should never want a preamp on 40m (unless you have a lossy antenna in which case the antenna would typically come with a antenna-mounted preamp).

The radio displays "PRE" when the gain at the center of the panadapter is >5dB.  If the gain is <5dB, the display will show "ATTN".  If the gain is between -5dB and +5dB, the panadapter shows "---" indicating that there is not much gain or loss in the current band.

Edit: also, the exact place where the indicator changes varies by radio as determined in the calibration of the preamp circuit.