When Operating system is deployed, it uses WinPE and WinPE does not have any Configuration Manager client installed. So it cannot access the resources using SCCM client account.
So you need to make sure that WinPE can access all the contents to execute particular Task Sequence and all specified shared folders etc. To access the resources, a separate Network Access Account (NAA), which WinPE will use to authenticate to Configuration Manager. This way Win PE can access the content it needs.
In Configuration Manager Console, Go to Administration > Site Configuration > Sites.
Select the Required Site Server
Right Click on Configure Site Components and then Software Distribution
Go to Tab Network Access Account
Select Specify the account that accesses network locations
Click OK to Finish
This completes adding the NAA to Distribution Point.