Last night I spent all the mana runes I bought and earned
yesterday and today (a lot more than 20000)
to upgrade the new Nissa from level 37. Afterwards, the game displayed
the confirmation screen and showed me how much the Planeswalker was
upgraded and how her skills had improved. This confirmation screen
couldn’t be left, though, so I had to close the game. After loading it
again, Nissa was back or still at level 37 where she had started out. Even giving
her 450 additional runes didn’t force her to update to where she should really be.
Support hasn’t provided any meaningful answer yet, let alone fixed anything.