Hi @Nithya_01 and welcome, it’s a pleasure to have you here! 
Thanks for asking the HubSpot Community!
I can see in this article “Create sync properties that copy data to associated records” that depending on your HubSpot subscription, there is a limit to the number of sync properties you can create. Is that what you are experiencing?
Which type of error are you getting, please?
The more info, screenshots (without sensitive/confidential information), and details you can provide, the better the Community can assist.
Also, I’d love to invite our Top Experts to this discussion: Hi @Phil_Vallender, @ScottPennwood and @Ian_Matt do you have suggestions to help @Nithya_01, please?
Have a wonderful day and thanks so much in advance for your help! 
Bérangère