An unrecognized expression appears in a script block. Script Expression: [field_name]

Question

When previewing my email I get the following error message:

An unrecognized expression appears in a script block. Script Expression: < MemberID: XXX JobID: 0

The error appears to be related to the field Lead:Language__c, which I can confirm is listed as a column in the Data Extension. I reviewed the article below that suggested removing the Lead: fixed the issue, but this did not happen for me. The AMPscript is listing below. Also, there are other variables in the email, but the language one is the only one using AMPscript logic. Can anyone spot what I've done wrong here?

AMPscript error in email - Unrecognized expression appears in a script block

%%[
    SET @salutationLanguage = Lead:Language__c, 
    IF @salutationLanguage=="de" or @salutationLanguage=="German" THEN
]%%

Sehr geehrte Damen und Herren

%%[ELSEIF @salutationLanguage=="en" OR @salutationLanguage=="English" THEN]%%

Hello

%%[ELSEIF @salutationLanguage=="sp" OR @salutationLanguage=="Spanish" THEN]%%

Hola

%%[ELSEIF @salutationLanguage=="Dutch" OR @salutationLanguage =="nl" THEN]%%

Hoi

%%[ELSE]%%

Hello

%%[ENDIF]%%,

Answer 1

try like this

%%[SET @salutationLanguage = Lead:Language__c]%%
%%[ IF @salutationLanguage=="de" or @salutationLanguage=="German" THEN]%%
  Sehr geehrte Damen und Herren
%%[ELSEIF @salutationLanguage=="en" OR @salutationLanguage=="English" THEN]%%
  Hello
 %%[ELSEIF @salutationLanguage=="sp" OR @salutationLanguage=="Spanish" THEN]%%
      Hola
 %%[ELSEIF @salutationLanguage=="Dutch" OR @salutationLanguage =="nl" THEN]%%
     Hoi
    %%[ELSE]%%
       Hello
      %%[ENDIF]%%