The aid they where bringing were those items banned by Israel in it’s collective punishment of the people of Gaza.

Gaza has been under severe Israeli restrictions, preventing all exports and confining imports to a limited supply of humanitarian goods.
There are delays facing the delivery of even the most basic aid. On average, it takes 85 days to get shelter kits into Gaza, 68 days to deliver health and paediatric hygiene kits, and 39 days for household items such as bedding and kitchen utensils.

Among the many items delayed are notebooks and textbooks for children returning to school. As many as 120 truckloads of stationery were “stranded” in the West Bank and Israel due to “ongoing delays in approval”.

Government schools were reported to lack paper and chalk, while the UN Relief and Works Agency, which supports Palestinian refugees and runs many schools in Gaza, was still waiting to import 4,000 desks and 5,000
items considered a “security threat”.
Other items banned from entering Gaza, coriander, pasta, fruit juice, toilet paper, chocolate, cigarettes, seedlings, school books and uniforms ,wood for construction, cement ,musical instruments,size A4 paper
writing implements,notebooks ,newspapers,toys.
Pasta, which had been forbidden in the past, is now allowed.

Hospitals and primary care facilities, damaged during operation ‘Cast Lead’, have not been rebuilt because construction materials are not allowed into Gaza.

Roughly 90 percent of Gaza’s factories are closed or are functioning at less than 10 percent capacity because of the inability to obtain raw materials and the inability to export finished products .
Rather than targeting armed groups, the blockade mainly hits the most vulnerable, such as children (who make up more than half of the population in Gaza), the elderly, the sick and the Gaza Strip’s large refugee population.

World Health Organization (WHO) trucks of medical equipment bound for Gazan hospitals have repeatedly been turned away, without explanation, by Israeli border officials.

Goldstone said his central criticism of Israel is that its strategy intentionally applied disproportionate force in Gaza to inflict widespread damage on the civilian population.
His report found that the Israeli air and ground attacks destroyed 5,000 homes; put 200 factories out of operation, including the only flour factory in the country; systematically destroyed egg-producing chicken farms; and bombed sewage and water systems. “If that isn’t collective punishment, what is?’’ Goldstone asked.’