Not Able to change the Effective date of BPA

 HI All,

 I am not able to change the effective date of BPA getting error 

"Please Enter an Effective From date that is not earlier than the Effective From date of the agreement"

Step to Reporduce:

• Copy the OLD BPA 
• Genrate new BPA with status "Incomplete"
• Click on Terms Button
• Change the Agreement control effective Date
• Gets Error
• Please Enter an Effective From date that is not earlier than the Effective From date of the agreement

Please suggest

Thanks & regards

Piyush Karankar