"Why are you all not helping?"
Translation:Warum helft ihr nicht?
Yes, as ikvilertalen said, it is the plural form. "ihr" is the 2nd person plural and "ihr helft" is the matching plural conjugation of "helfen".
ich helfe = I help
du hilfst = you help (singular)
er/sie/es hilft = he/she/it helps
wir helfen = we help
ihr helft = you help (plural)
sie helfen = they help