Not sure why this Validation is not working. The error says Syntax error found ‘)’

Question

AND(
    NOT(ISBLANK(Account.Name)),
    OR(
        AND(
            ISPICKVAL(LeadSource, "Web"),
            Lead_Source_Details__c <> ""
        ),
        AND(
            ISPICKVAL(LeadSource, "Referral"),
            NOT(ISBLANK(Referral_Source__c))
        )
    ),
    OR(
        Amount > 1000,
        AND(
            ISPICKVAL(Type, "New Business"),
            Probability > 50
        )
    ),
    NOT(
        AND(
            ISNEW(),
            ISCHANGED(Status)
        ),
        NOT(ISBLANK(Email))
    )

Additional criteria are being added to the section at the end to ensure that the contact and leadsource fields are not blank

    NOT(
        AND(
            ISNEW(),
            ISCHANGED(Status)
        ),
        NOT(ISBLANK(Email)),
        NOT(ISBLANK(Contact__c)),
        NOT(ISBLANK(LeadSource))
    )

Answer 1

Hello It looks like the syntax error in the initial validation rule is caused by a missing closing parenthesis after the last NOT function. Here's the corrected version:

AND(
    NOT(ISBLANK(Account.Name)),
    OR(
        AND(
            ISPICKVAL(LeadSource, "Web"),
            Lead_Source_Details__c <> ""
        ),
        AND(
            ISPICKVAL(LeadSource, "Referral"),
        ****NOT(ISBLANK(Referral_Source__c))
        )****
    ),
    OR(
        Amount > 1000,
        AND(
            ISPICKVAL(Type, "New Business"),
            Probability > 50
        )
    ),
    NOT(
        AND(
            ISNEW(),
        ****ISCHANGED(Status)
        )****
    ),
    NOT(ISBLANK(Email))
)

Regarding the additional validation rules, they seem to be correct and well-formed. You can add them to the existing validation rule by combining them with the AND function, like this:

AND(
    NOT(ISBLANK(Account.Name)),
    OR(
        AND(
            ISPICKVAL(LeadSource, "Web"),
            Lead_Source_Details__c <> ""
        ),
        AND(
            ISPICKVAL(LeadSource, "Referral"),
            NOT(ISBLANK(Referral_Source__c))
        )
    ),
    OR(
        Amount > 1000,
        AND(
            ISPICKVAL(Type, "New Business"),
            Probability > 50
        )
    ),
    NOT(
        AND(
            ISNEW(),
        ****ISCHANGED(Status)
        )****
    ),
    NOT(ISBLANK(Email)),
    NOT(ISBLANK(Contact__c)),
    NOT(ISBLANK(LeadSource))
)

This validation rule now includes all three additional criteria and will trigger an error if any of the specified fields are blank.