Is a person sinful if they do not accept a ceremonial meal invitation, and is it generally obligatory to accept invitations?

There is no objection to not answering a food invitation that is not a wedding banquet, as the majority opinion is that attendance is not obligatory. The hadiths regarding answering an invitation may be interpreted as referring to a wedding banquet, or that answering is a recommendation and a matter of preference. Answering the inviter's food invitation is good and recommended. Even if it is a banquet, there are excuses that permit non-attendance, such as suspicion about the food, singling out the wealthy, the presence of someone who would be harmed by one's attendance, an invitation out of fear of evil or desire for prestige, or to witness falsehood, or the presence of objectionable acts. Among the excuses also is for the invited person to apologize to the inviter and thus leave it. Even in cases where attending a banquet is obligatory, eating is not compulsory.