The mystery of unproductive on my Fenix 5 please can anybody help explain it

Hi All,

I'm guessing similar questions have been asked elsewhere on the forum but I can't easily find the correct section, so just punting this question out there.

Ok, so I'm baffled as to why I'm showing unproductive (I never thought one word on a device could be so depressing or morale damaging!!) I've had my fenix 5 for at least 3 years now, and recently I've been on a running streak of 24 or days, ranging from 3k to 10k everyday. My hear rate has been in in threshold for the majority of the time for each run and it's telling me that my fitness level is optimal. However for the last two weeks it's been reporting unproductive. I have no idea why, all the other indicators on the watch are telling me it should be productive. I've tried running a little further and little less to mix it up a bit, but still no change. Anyone have any clues as to why it should still be giving the unproductive. After having the watch for a good while now and being a regular trail runner I must confess the prod/unprod stuff still seems like a black art to me, I'd love to be able to fully understand it and use it to its full advantage.