The most likely situation is; you achieved full member rank before the through activity before the launch of the merit system. You either had some posts deleted before merits were airdropped or your activity calculation before the event made you eligible for only 10 airdropped merits, hence the drop in rank, and disabling of the avatar feature.
Avatar feature would only be available again when you get to full member rank.
N.B. this topic belongs in Meta, you should bump your old thread.
I agree, 108 activity or post it might be deleted before the merit system is implemented. Since he doesn't have 120 posts even at this moment we could assume that it is deleted.Do i have to be full member in order to edit my avatar again or do you have a clue how to fix this? Please help me 
Thanks guys in advance.
You were adivsed in this topic you made last year to message an admin to manually remove the existing avatar.Thanks guys in advance.
Avatar feature would only be available again when you get to full member rank.
N.B. this topic belongs in Meta, you should bump your old thread.
Ranking down when your post is deleted never happened to me but for sure it is what's gonna happened if you don't get the requirement to rank up. Anyway for sure if you're active in the forum you could work it out how to earn merits and rank up again
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