Missing spell slot

[Dragontail]

a level 2 sorc just became level 3 after latest session, he dragged and dropped the sorc to his class bumping him to 3rd but it did not add the spell slots correctly (should be 4/2 and is 3/1)
any ideas on why or how to fix?

[Zacchaeus]

Click on the mode button at the bottom of the actions tab until it shows 'Preparation' and you can alter the number of spell slots in the box that opens up.