Resource allocation not created for certain projects

[StephenPMO]

We moved from resource plans to assignments a few months ago.  We noticed recently that there were numerous resource assignments that did not have allocations.  One of our developers ran a script to update each of the resource assignments and most were corrected but we are left with 17 records that cannot be updated.  Even creating new resource assignments for these projects does not create an allocation.  See screenshot for an example.

What should we do?  Thank you in advance.

[StephenPMO]

This is the error message I get when I try to update the assignment although there is no resource plan associated with the assignment and dates are within the project plan.

[miftikhar20]

Hello @StephenPMO, 

It looks like a date validation issue. Even though you’ve moved to Resource Assignments, ServiceNow still enforces strict validation against the parent Project timeline. The system will refuse to create Allocations (capacity/financial records) if the assignment date range falls outside what the Project record defines. 

To fix the issue try the following:

Option 1: Extend the Project Dates  
If the work is legitimately occurring outside the current project window: 

• Navigate to the Project record. 
• Update the Planned End Date, so it fully covers the Resource Assignment dates. 
• Save the Project. 
• Return to the Resource Assignment and update/save it again (or rerun your script). 

Allocations should be generated once the timelines align. 

Option 2: Shorten the Resource Assignment 
If the Project dates are correct and the assignment is outside the valid window: 

• Open the failing Resource Assignment. 
• Adjust the Start Date and End Date so they fall strictly within the Project’s planned dates. 
• Save the record. 

 If my response helped, please mark it as the accepted solution so others can benefit as well.    

[StephenPMO]

Project planned start date is 10-27-2025 12:00:00.

Project planned end date is 04-27-2026 11:00:00.

I associated my resource assignment with a project task that has these dates to be sure it's well within the timeline of the plan 

Start date 03-12-2026

End date 03-12-2026

Still getting the same errors.

Alert level: critical.  Resource cannot be allocated after current Resource Plan's End Date

Alert level: critical.  The request cannot be processed because resource plan dates are outside the project planned dates (10-27-2025 - 04-27-2026). Update the resource plan dates, and try again.

[StephenPMO · Accepted solution]

I fixed my own issue simply by doing the following:

1. delete the existing Resource Plan(s) on the project
2. change the effort on the existing resource assignment(s) and Save OR
3. delete the existing resource assignment(s) and recreate