When you try to import multiple resource assignments and, if resource allocation for one or more resource is not specified (assuming that the system would automatically allocate 100% to the users) then, those task assignments may not get imported.

In the Resource_Names column where you have entered multiple resource assignments and have specified allocation for one of the resource assignments, but not for the other resources listed in the file.

When importing multiple user assignments and, the allocation is specified for one of the resources, make sure you specify the allocation as 100% for the other users instead of leaving the field blank (if you are not sure of the exact allocation percentage).

If the following entry is listed in the Resource_Names column of the CSV file:
User1,User2,User3[25%] In this example we are trying to allocate 25% to User3 and 100% to user1 and User2 without specifying it.
The import would be unsuccessful unless 100% allocation is explicitly specified for User1 and User2.