Got a 2 week extension but PIP terminated before agreed date

Please can you help. My son in law is Appointee for his daughter. I always do his daughter’s paperwork. He received full pip review pack dated 2nd June stating to be back by 2nd July. The pack did not arrive until 14th June. I knew I did not have enough time so asked him to request extension. He did and was given extension til 16th July. He got a name and asked for acknowledgement by letter but was told he would get an text, which has not arrived..

On Friday 4th he received a letter saying paperwork was not received by 2nd July. He finally got through today to explain that he had a name of the person who gave him the extension, but was cut off. Does that mean his daughter has been knocked off PIP? If so, is there anything we can do. Thank you.