Taliban is insisting on constitutional reforms such as mentioning the word "sharia" in the Afghan constitution. Currently, the constitution refers to "Islamic law" instead of "sharia" specifically. However, including the word "sharia" would present challenges for donor countries, whose constituencies may be averse to funding a government that is constitutionally required to implement sharia. On the other hand, if the word "sharia" is not incorporated into the constitution, the Taliban would see this as a major defeat.
Read about all the obstacles to peace in Afghanistan's war:
The Taliban and obstacles to Afghanistan peace talks
Source: Al Jazeera