If you see this message when making a web request, there are not enough slots for that assignment to allow that request to go through.
To Resolve This Issue:
Remove/Delete existing web requests for that assignment on that day to allow the new request to go through.
Add additional slots for that assignment
a)Administration -> Setup -> Assignments section
Select the assignment on the left hand side and select Edit.
You may select the date on the calendar to add more slots for that particular date by selecting [Add] New recurring pattern
Add how many slots you need for this date in the Allow At Most field and select Just For This Day.
Click on Save on the top right hand corner.
You can select the Pattern check-box on the left hand side. Edit that pattern to increase all slots with the new number of slots.
Enter the new number of total slots for this assignment in the Allow at most field.
Click Submit to change the number of slots for the entire pattern.
Save top right hand corner.