Multi-IF seems to fail

I am trying to use a status field (Ability) to enable the calculation on a formula field where if another date field (Repair Completion Date) is set, it will find the days between that date and the Damage Date then multiply by Holding Cost, and where Repair Completion Date is not set then it will find the days between Damage Date and today then multiply by Holding Cost. My formula is below, each unique part parses correctly, just not all together for some reason!

IF({Ability}="Unusable",IF({Repair Completion Date},((DAYS({Repair Completion Date},{Damage Date}))*{Holding Cost}),((DAYS(TODAY(),{Damage Date}))*{Holding Cost})),"")

Hi Chris,

Can you let me know if this works? I cleaned up and simplified your formula. Nested IFs do work in I didn’t discover exactly what was wrong with yours because I decided to remake it in a slightly different way.

  {Holding Cost}*DAYS(
      {Repair Completion Date}="",
      {Repair Completion Date}
    {Damage Date}