The post, which includes internet orders that never arrived, had been held in Jordan since 2010 and was released under a one-time agreement.
Palestinian postal workers in the city of Jericho are now faced with sorting through more than 10 tonnes of goods.
An official told AFP it would take another two weeks to sort and deliver.
Ramadan Ghazawi, who works at the post office in Jericho, said the items appeared to have been blocked on security or administrative grounds.
Israel controls entry to the West Bank via the border with Jordan.
In a statement issued on Tuesday, Palestinian Authority Communications Minister Allam Moussa accused Israel of having failed to implement a memorandum of understanding signed in 2016 that would have allowed international mail to enter the Palestinian Territories without first going through the Israeli postal service.
The Israeli military’s Co-ordinator of Government Activities in the Territories (Cogat) told AFP that an agreement was in the works but gave no further details.