Hi Carmel,
We tested at my end by using the formula you provided above, =IF([RevisedResponseTargetDate A]="","",IF(AND([ResponseSentDate B]="",[Column C]<[Todays Date]), "No",IF([ResponseSentDate B]>[Column C],"No","Yes")))). We got syntax error if we set ResponseSentDate, RevisedResponseTargetDate and Todays Date as Date and Time type. Moreover, there are only 3 items in this formula so I think column C is missing in it.
Moreover, we created another 4 single line text columns named A,B,C and D with a Calculated column named RESULT. Here is the formula and the result we got:
I would like to know the column type you are using cause there is no related calculations for Date and Time column. For your reference: https://support.microsoft.com/en-us/office/examples-of-common-formulas-in-lists-d81f5f21-2b4e-45ce-b170-bf7ebf6988b3 It may need some complicated to meet your requirement.
Best Regards,
Ivy