Trouble retrieving "Then" clause in If condition

Hey Community! This is my first time posting so any suggestions over mistakes are welcome

I am using a simple If statement with multiple clauses. The issue I am having is two out of the three clauses are working but one of the clauses is not returning the "Then" statement.

It looks a little like this.

=If [Last Year] =0 AND [This Year]=0 Then 0

ElseIf [Last Year]=0 And [This Year] >0 Then 100

Else (([This Year]/[Variance]*100))

The first and last clauses are returning proper values, however the "ElseIf" clause is not returning "100" where necessary. Instead I see 0.

Is there issues when using multiple If Then statements? Is there a different form of formatting that can be used?

Any help is appreciated.

Thanks!!