If you have never signed in
Maniaplanet 4 accounts only!
Maniaplanet 4 (released May 9th, 2017)
was not imported from Maniaplanet 3
, therefore you cannot reset your password from this
You need to download and install the Maniaplanet 4
use the ingame password reset feature:
Select profile > Create a new profile > Sign in > I forgot my password